There is no more effective maintenance procedure than using keyboard memory and MP. Make a habit of playing in your mind at every opportunity you have. The difference between a good memorizer and a poor memorizer is not so much "memory power" as mental attitude -- what do you do with your brain during your waking and sleeping hours? Good memorizers have developed a habit of continually cycling their memory at all times. Therefore, when you practice memorizing, you must also train your mind to constantly work with the memorization. Poor memorizers will require a lot of effort at first because their brains are not accustomed to automatically perform memory functions continually, but is not that difficult if practiced over an extended period of time (years). Once you learn MP, this task will become much easier. Savants generally have problems of repetitive motions: their brains are cycling the same activity over and over again at all times. This can explain why they cannot perform many normal functions but can have incredible memories and amazing musical abilities, especially when we view these savants in the light of our above discussions about memory and playing music in your mind.
Maintenance time is a good time to revisit the score and check your accuracy, both for the individual notes and the expression marks. Since you used the same score to learn the piece, there is a good chance that if you made a mistake reading the score the first time, you will make the same mistake again later on, and never catch your mistake. One way around this problem is to listen to recordings. Any major difference between your playing and the recording will stand out as a jarring experience and is usually easy to catch.
A good maintenance procedure is to go through the process first used to learn/memorize the piece, such as starting from arbitrary places, playing very slowly, playing cold, etc. Make sure that you still remember it HS. This can become a real chore for major pieces, but is worth it, because you don't want to find out that you need it during a performance. These HS maintenance sessions are not just for memory. This is the time to try new things, playing much faster than final speed, and generally cleaning up your technique. Extended HT playing often introduces timing and other unexpected errors and this is the time to fix them by using the metronome. Therefore, playing HS for both memory and technique enhancement is a very worthwhile endeavor. The best preparation for recovery from flubs during a performance is HS practice and MP. Then, if you flub or have a blackout, you have many options for recovery, such as: keep on playing with one hand, first recovering one hand, and then adding the other, or just keep the melody going.