I dunno, I'm just looking for some practical advice and wondering if I'm "bobbing in the shallows" because I'm not putting enough effort in.
I always need to say this before I talk about momentum and stream entry, but the way I got Path was probably quite different to most people. I had never worked with insight practice in the way it's practiced Buddhism, but had been inadvertently observing the 3C's, with emphasis on impermanence, for about two months solidly prior to getting Path, which I didn't even realize at the time until I found this site. So, in my experience, and as I understand it from the practices of others on here who've done it, momentum is essential to eventually flipping it and landing Path.
You're training your mind to observe the fundamental nature of reality in all it's impermanent, empty and tension-packed glory; if you're only doing that seriously for 30-40 minutes a day then it's going to take you much longer than, for example, someone who's doing 2-3 hours of sitting per day
and bringing their practice into daily life. I'd also include consistency of practice as well as momentum, doing sloppy practice for four days out of seven is pretty useless, but if you can ensure you're noting and observing phenomena accurately, to the point where you're able just incline your mind towards seeing the arising and passing of anything in the sense field, then you'll stand a far better of chance of getting it.
Think of it this way: To get stream entry, you basically need to see what it is that still implies an "I" observing this experience; there are a finite number of possible "points of entry" where a sensation can be observed, and a, seemingly, infinite range sensations observable by the human body. Dan used the analogy of "shooting aliens" in MCTB, which is quite a useful way to think about it, you're basically 'shooting' sensations with a 3C's 'lazerbeam'.
Useful? If not, ask away and I'll see what I can suggest - It's entirely possible, and that's one of the most important things to remember, don't give up or allow yourself to feel defeated 'cause it's all just more of the same transient, empty sensations.
Btw, I'm actually writing up a response to your question about intent so I'll post it in that thread when I'm done.