There’s an interesting article on the Bulletproof Musician blog discussing a study that compared the effects of learning and revising at different times of the day. One group learned in the morning and revised in the evening; the other learned in the evening and revised in the morning. The results suggest that the second method is better.
The reason put forward is that sleep enhances the learning process, and learning last thing at night means that there’s less interference from the day’s other activities. The study also showed that those in the second group were able to get up to standard in their revision session in the morning quicker than those in the first group.
I’m going to try to arrange my own practice schedule like this. For half an hour before going to bed I’ll practise more difficult aspects of playing, such as technique and troublesome passages in my repertoire, and as soon as I get up I’ll revise what I did the night before. I’ll still try to do half an hour or so throughout the day.