How do you cycle practice pieces?

I as a kid I had great teachers and picked up piano fundamentals pretty fast. I stopped piano lessons after middle school. After years of on-and-off practicing learned to play 85%-95% of grade 7-8 pieces correctly through sheer determination (I can nail grade 6 or below pieces). As I'm not too obsessed over the last remaining part. Being an adult with responsibilities and commitments really reduces my amount of practice time. Over the years I stopped improving my technique, and focused on expanding my repertoire. This is due to time constraints and not being able to get my full money's worth out of intermediate/advanced piano lessons.

Now I have this problem where I need a whole practice session to "relearn" a piece. I have so many pieces to relearn, but when I cycle through or pick only favorites my ability to play the other pieces start to slip. Should I forget some pieces, or is there any advice you can give to maintain a bigger repertoire?