It makes a great deal of sense to me to break a piece up into sessions, and only work on one session for 15-20 minutes. But let's say I've got a piece broken up into however many sections, and I work on section one for the first 15 minutes. Why move on to the next piece for the next 15 minute session, why not do section two of the same piece? It seems to me that you suggest only working on one section of a piece per day, have I misunderstood your method?
Up until now, it seems like I can't really more on more than three pieces at once (or three pieces a month.) I have been doing Czerny but am planning on cutting him out (you've won me over on that one!) So that would make it 4 pieces. (At and before Christmastime I manage to work on about 10 pieces, but these are all Xmas songs and most are fairly easy, and very familiar). Oh, and I have a repertoire of about 6 pieces that I play regularly enough to keep them current.So finally, here's my question: Excluding Xmastime, and taking into account what I've just said above, how many pieces do you think I can/should be able to work on a month with a 90 minute practice routine?