The difficulty at this stage--well, with any stage, really--is to sustain freshness and alertness while doing what you have to do to keep a piece internalized. In order to be fresh and alert, you need to keep some variety in your practice. Otherwise, you might find yourself in thoughtless routine, and that could lead to some unfortunate surprises when you bring your piece out in public. Because I'm least motivated when it comes to mental practice, I find that this is the area where I have to be the most conscious about finding variety in my practice.
If I'm short on time or I really feel confident about a piece, I'll just review the starting points of each landmark. From there, I might go to play the piece directly. (I'll write about playing techniques for this stage in my next post.) Generally speaking, my mental work at this stage takes less time than the playing work--but that doesn't mean it's no less important.
As I become more and more confident in my mental work and the playing of the piece, I might alternate days of mental work and days of playing work. This is not so much about time constraints as it is about keeping things fresh and varied. Also, by taking a day off from playing in favor of a day of mental work, new interpretive insights will emerge from the silence.
There's really an endless variety of ways to diversify your mental practice. The most important thing is to keep it varied and to make sure that your choices are conscious. For those reasons, I continue to work with a practice log, a timer, daily goals, a metronome...you know, all of those good habits. This isn't to say, however, that I don't enjoy the occasional unplanned mental practice session on the beach, in moments of insomnia, or in walking meditation.
With so many options available, what are some other mental practice techniques that you can think of? Post your comments here!