Matthew, to reply in the same spirit.

The difficulty in answering your question is that Arhat is no longer a simple concept, but something that means different things to different people.  Some of these things include:

1. Somebody who has followed the path of insight to the end.
2. Somebody who has followed the noble eightfold path and the training of the sangha to the end.
3. Somebody who additionally has semi-magical attainments from strong concentration.
4. Somebody who additionally has saintly morality.

From reading the Suttas, or later Buddhist doctrine, you might think it was all of 1-4.  However, another view (and perhaps relevant to the DhO) is that it is just (1) that is is necessary.  Everything else is incidental - or at least need not be attained to the same degree. Just as our farming techniques have improved from 2500 years ago, so the methods to achieve awakening might be thought to have improved from 2500 years ago, particularly given the thousands upon thousands of talented people who have followed in the Buddha's path and kept the wheel of the dharma turning.

However, if you merely discuss (1) as the means to Arhatship, you might be regarded with scorn by people who think it essential have saintly morality, or to wear a specified robe and carry an umbrella instead of a poncho, or to abandon the craving after elephants and bondservants. So the discussions are inevitably fraught, depending on how people choose to define Arhat and which of these criteria are met.

But ... the noble eigthfold path is a fabrication. Dhammadinna clearly says this in the Culavedalla sutta, and it is the experience of many on this forum. You must follow the underlying principles of morality (calm), concentration and insight, but not the specifics oultlined in the suttas. Remember, the suttas note that the magical attainements are a dead end, and not the objective. Also, morality is a training, not an attainment.

Daniel made an incredibly useful comment on this - that there no end to the paths of concentration and morality, but there is an end to the path of insight.  Many reports on the DhO (and elsewhere) show people achieving this end to the path of insight. A long path of training and development, through many stages, eventually leads to the final event associated with the complete letting go, and then the attainment of not-self that destroys clinging (and the desire of the mind) without residue. Those who achieve this can read the suttas, and see that the experience is exactly what the Buddha taught.  However, they are also able to discriminate between things in the suttas that are essential to the path of insight, and things that are incidental or culturally bound, and so not to be taken as seriously.

This was the point of my joke before,  My joke was dharma - saying that saintliness is not necessary for the Path of Insight.  And also, clinging to saintliness is still clinging.

Best wishes

Malcolm 
(Asshat)

EDIT:// sry for wall of text

To experience Nibbana you need to have jhana even if Nibbana is not jhana by itself but more like absolute background to everything which mind need to experience from time to time to not suffer (you can think of it as something brain need to do with its neurons for them to not get tired or rather to keep their physiology, they just need to reset from time to time basically). Normal non-jhanic mind also have its own strategies to get Nibbana and normal non-meditating people do experience Nibbana internally as well though by different methods and as long as this mechanism work they feel well even if these methods do not make them experience Nibbana like jhanas allow you to experience. In real time.

Even 1st will shift strategy of mind to reset neurons and actually it nice mind state, though it is hard to stabilize by itself because it is not very transparent and is on the border of normal state and other jhanas. 2nd jhana is much more stable as it just keeps itself. The one way 1st jhana can be stabilized is using higher sub-jhanas which are easier to change as your mind if anything operates on base layer and thus is concentrated on it and with it being concentrated on first layer the second can naturally shift its jhana mode to higher jhana. These layers do change like buffers in double buffered rendering but you won't notice it because it happens seamlessly. If anything my initial assumption was that you experience something like 1st jhana and 4th sub-jhana and with that can also can experience Nibbana and because of that 4th sub-jhana you have this interrest in Arhats because it resonates with how Arhats generally tend to be. They do however seem to be in 4th jhana and any sub-jhana, usually formless so more refined mind state.

If you are unfamiliar with this sub-jhana terminology Daniel describes it in MCTB2. I have not really read it but I remember him talking about this stuff and from what he was saying it matched my own view of these mind states which I also found can be stacked and did it separately. When two experiments confirm the same model I tend to accept it as working model, like with science.

In any way 4th jhana is very transparent, almost like it was not there at all but it still generates the required experience of Nibbana and thus can be used as sub-jhana to stabilize lower jhanas. When mind learns jhanas and unlearn to experience Nibbana through strategies normal mind uses it will be actually much easier to have higher jhana mind states than even lower jhanas. This is why anything like an Arhat is possible. Arhat won't use normal mind at all because he/she switched to use jhanas exclusively and in this way of using brain it is easier to use higher jhanas thus default mind states for them are these higher jhanas. I like using 8th jhana the most and create my custom mind states with it which uses even different strategy to accomplish the same Nibbana effect but not being even what you normally think of as Nibbana.

It is even possible to just learn to trigger Nibbana by itself and have any mind state regardless of how it does reset brain or just when you feel something is up or just intuitively do it all the time.

Models, jhanas, paths, etc. are just some frameworks to organize things but in the end what really matters is if you can keep internal states of your nervous system and properly maintain its homeostasis. As long as your neurons are happy everything will feel nice and dandy as well. What strategy is used doesn't really matter that much and there are many strategies. Because in Buddhist framework we have jhanas and Arhats are supposed to master these jhanas then it would make sense for Arhats in this tradition to use jhanas as their default strategy, otherwise why even bother with all of this? Normal person who does not know anything about jhanas, paths, Nibbana, etc. can intuitively keep his/her mind in proper shape as well. I see you intuitively feel that all this enlightenment would not make any sense if it was not somehow permanent. I will try to break your bubble right here: this idea of never ever suffering is only agitating your mind and make you suffer more and is completely unattainable. Buddha did suffer from time to time as well and he knew that by his models he should not be able to. But he also knew how this works. The difference between a Buddha and normal person is that Buddha know dozen of methods to make himself not suffer once he recognizes his/her suffering and normal person does not thus normal person is forced to wait things out (or panic or use emotions as their method) and Buddha can do something meaningful and skillful about it. Arhat is by definition someone who knows subset of what Buddha knows, most useful stuff. Arhats however are also Buddhas as they do invent their own methods as are actually all people who took time to figure how to make themselves feel well.

Then again if Buddha had head ache he would just take aspirin and not try to fight it off using cessation of body and mind. Well, usually at least. Buddhas know stuff because they try to break stuff with their heads, but then it is their practice and not really suffering. When you practice in order to overcome suffering by inventing stuff you do not really suffer and take strange satisfaction from the practice itself. Only followers suffer when they are supposed to replicating something XD

From your post I get that you are not so much doing jhanas but learned how to experience Nibbana directly. Could you tell me how this differ from 1st jhana? There is a difference but not that great actually and I ask this to make you think about it. Maybe then you will realize how close you are to hitting 1st jhana all the time in your normal waking state.