It is a nice one, indeed. Yes, can agree actually that it is beautiful, not just nice :))
Muscle memory. To some extent, it stays, yes. but again depends on how well you played it before, how well was it learned. You see, your father also needed time to gain back the agility, well, we dont forget them completely and we have some learned skills, but yes it takes time.
For me, the easiest part is to refresh the memory from scores, the reading-playing part is not that problematic. The real trouble is that I realized I can not play some extremely very hard compositions I play at your age :(
Even if I would practice every day, for some hours I would not be able to play them as before. My arms would be tired, I would have to go very slowly remembering it, slow soft practising and it would take a double of time or more. And in the end, I will not be able to play those really hard ones, no sufficient technique right now. That is frustrating hahaha
Well, I don't find it hard to forget the songs that I rehearse a lot for a while, of course, if many years go by I might forget them 😆.
You will see one day. Now you don't even have many years on your life counter :D You are still under 19 or 20 lol so it doesn't count 😂 🤗