are Bach pieces much harder to "keep in shape" once learned?

I've had the opposite experience. The first Bach I learned was probably way too hard for me at the time. I began my first fugue (three part) when my husband was in the hospital recovering from heart surgery and I really needed something absorbing to take my mind off of things. I'd go to work, (had to, I'm the breadwinner) go to the hospital, stay with him until closing, come home and do unspeakable things to Bach until I was wound down enough to sleep. Learning under battlefield conditions like that, and working so very hard at it, that piece in particular has stayed with me. I may not ever play it very well but I doubt I'll ever forget it.

I find Bach harder to learn in the first place, and pieces that take me longer to learn usually also take me longer to forget. I've never actally tried to keep up a Bach piece, though, so I'm not sure.

I find that pieces that are near the top of my skill level are hard to keep up, which makes sense. I finally had to let the Brahms Rhapsody in G minor go because I just couldn't keep it anywhere near playable and also learn new pieces. I have four pieces in my permanent, memorized repertoire now, and that might be my limit.

Nancy