Hello  i practice vipassana mahasi style for some time did some retreats and read a lot of matieral about vipassana  but still there are some
questions i coudlnt find the answer to  - which are :

1 . What is the shortest time of noting which gives some "benift" - what i mean is i always read how important it is to have a constant practice 
without "stops" how important it is to have awreness without breaks - so this made me wonder : whats the limit when a noting becomes "usless" 
does a 5 minute meditation (mahsi style-straight to noting) have any value, does it advance me in any way to gain insight ?
what about noting a single thing (like an itch or sound)  or just noting a single movmet like lifting the arm or lowering it ?

2 . How much space can there be between noting before starting to lose insight ?  for instance if i do a 5 minute meditation once in a weak does it have some benift or is it lost ? what about a 2 hour meditation (one walking one sitting) ? what about noting a single thing in a week : a single
itch or a single thought ?

3 . How the proccess of ganing insight work exactly ? i mean in more detail than : "you watch things are they truely are - you see the three
characteristics of reality (anicca,anatta,dukkha)" but in a more detailed way as what exactly happens after you watch something ? which relates to the previous questions - when i watch something does this get stored "somewhere" ? or is lost and only if i have enough concentration it is
worth something ?

4.  How the proccess of ganing insight progress eaxctly (i read about the progress of insight but im asking : exactly) ? how do we move from one nana to another ? is there a certain amount of time we need to be in each nana ? im a bit confused about this cause i read different theorys - a teacher told me something like we at daily life always expirence different nanas - in individual events where we can expirence the 3 nana and than the 5 and than the 3 -   on the other hand in my practice a teacher gave me different instructions when i move from nana to nana - assuming a nana is a
stage - and once i get to the 16 nana i retrun to the 1 nana - and he "advance me" throw them the same when i meditated 20 mins or an hour   and now at dhamma overground i read something as if this stages can take a big amount of time - so i am very confused 


no need to answer all - you can only talk about one point if you like - anything helpful is appreciated long or short posts -  this are questions i had since the start of my practice (something like 3 years) and i still didnt find an anser to them . so anything someone wants to add here ... the better