personally for me, it took about 3 summers to get where im at, and thats a fairly basic level, tantrums, backrolls, 3's, etc. there are so many factrs that determine your progression though, frequency of riding, obviously if you ride every day youre gonna get the hang of it pretty quick. obviously if you have a wake boat you will progresss faster, however i ride behind an 18 ft sea ray w/tower, and thats just fine to do what im doing. another thing is that some people, for some reason are just naturals, and learn new tricks faster than others, for me what it all comes down to is willingness to learn, threshhold for pain (yeah water does hurt) and overal attitude. be positive, id love to be riding behind an xstar or wakesetter, but hell i dont have $70K just layin around haha, so be happy with what you have and just ride.
ps- i learned my heel w2w and 1 wake TS 180 behind my 16ft fishing boat. Learned my w2w TS jumps behind a freakin jetski haha