The deadlines I have to meet are usually about 1 week or less, so you are forced to get the max out of yourself, and not put pieces on the back burner.
Some may think that this is a fairy tale, but it is actually the norm in top musical institutions virtually all over the world. The principle is, of course, that you want to do something that is as close as possible to your sight reading level and that you have a good enough technical background, so you don't have to struggle with material things like "tempo".
In this
interview clip (at 5:40), Cyprien Katsaris talks about how one of his teachers, Monique de la Bruchollerie - a great pianist in her own right -, required him to learn:
1. Chromatic Fantasy and Fugue - Bach
2. Sonata opus 110 - Beethoven
3. Rachmaninoff Paganini Rhapsody
within ONE week! If you are not really ready for it, then 18 hours a day every day will not even be enough to get that ready. Of course, he was ready, because he could already play the Tchaikovsky.

P.S.: He also talks about the technical regime of scales and octaves he had to go through every day, and the interview is overall very useful to watch. For example, he requires students to solve all kinds of problems in his presence, right on the spot and without delay, which I think is a fantastic approach, especially since (judging from his master classes) he NEVER humiliates the student; always gives them time and space to do so.

EDIT: It's simply amazing and rather funny how hard and how long many people (including myself before I was taught to see the light) are prepared to work to avoid a couple of minutes of discipline to do things the right way.
