Just play threw the piece(s) every single day?
How long do you think a day is?
Well its long enough to practice about 1-2 hours of music isn't it?
I thought the subject was "100% right over time?". not every single piece a pianist has learnt at an advanced level over massive periods of time. I was talking like 20 pieces maximum to memorize. Its realistic to memorize lots of pieces for say a concert, then play them at the concert. But after the concert is done you will most likely forget most of them as you move on too new works. If we are talking about maintaining that quantity at a high level, then forget it.... Even if there was 100 hours in a day it wouldn't make a difference because the amount of time and focus it would require to keep that amount of pieces in your memory would prevent you from learning new pieces and progressing, its as simple as that really.