Austin is now 3 weeks (22 days today) and has been "growth spurting" since Monday. pertty much what you describe! He still sometimes goes as long as 3 hours between feeds but often its only 2 and sometimes just 1.5 hours. He also varies between 15-20 mins one side, up to an hours feed, feeding from bith sides.
There is no pattern to it, and I can't predict at all what he will do at each feed! I am assuming that he is still working out for himself how much he needs!