ranjit What do you mean by "efficient" though? Do you think you would have spent less total time on the Beethoven A minor major if you learned it over a period of a few weeks? Do you think it would have been learned better? How do you make that call?
Just after I had learnt it quickly for the first rehearsal, I wasn't at home with the piece. Yes, I could play through it with the cellist, but it still needed to ripen. I couldn't tell you now how much longer I worked on it before feeling I knew it well enough to play in a concert: I suspect it was about as long as I would normally take for such a piece anyway.
ranjit What is your approach when you have more time? Do you work on say 100 measures a day in parallel for a week? Do you sight read multiple times? Or do you perfect measures like johnstaf outlined, 12, 23, 34, combine?
I sight-read once, or maybe twice, but not more than that. I want to get the feel of the whole piece, to see the big picture, but after reading through a couple of times I need to go into detail.
I take the time to go through the whole piece slowly, putting in fingering. Once the fingering is sorted out (I know I will probably change some of it later, but I need a first version), I isolate what seem to be the hardest parts and work on those first. I don't have a fixed routine: as I discover the piece in more detail I find different passages that need special attention: depending on the complexity I'll divide those passages into smaller or larger chunks and work on progressively tying them together. If it's chamber music I know I'll be playing from the score, but there may be technically difficult passages that I need to memorise, so I'll work specifically on memorising those.
I was very interested to watch the videos of Molly Gebrian and to find out that I already used many of the techniques she recommends: taking frequent breaks, working on different pieces in parallel, practicing a particularly tricky passage in the evening and then again in the morning... I don't make a schedule: I rely more on my feeling to decide how often to practice a particular passage once, twice or even three times a day before giving it a rest for a few days.
ranjit I guess the question then remains: How do you determine when to take a break? If you get into a "flow" state for 2-3 hours and don't feel a lapse in concentration, do you keep going, or do you throw in a break there? Do you sometimes push your ability to concentrate by keeping at it? Or do you always use your internal sense of when you feel like you're losing concentration?
I rely on my internal sense, and that sense tells me to take breaks quite often. Maybe I take a really short break after just a few minutes, or a longer one after half an hour. The only times I push my ability to concentrate are when I consciously decide to play through a whole piece.