I believe that without a doubt there are songs that even though you spend a long time without performing them, they will always stay in your mind, maybe you will never forget them, now, the point is that the mind and the body must also be in tune, so practice will always be essential at least if you want to perform that song perfectly.
It happens in all areas, an athlete will always know what to do to excel and perform well, but the issue is that the body responds to their demands, so no doubt the practice is essential as well as the years that has the body, the latter is certainly important.
Your question about if we forget the pieces with the passing of time depends on the complexity of the piece, at least in my case; if the song has simple chords and a simple tempo, I will probably never forget it even if I don't practice it, I think that each song is particular in that sense.
From my point of view you have executed this song very well, I would have no observations about it haha, although maybe you internally are not very happy.
I was also happy with how it turned out :) I said I will not reveal am I satisfied or not, until a bit later :))) Thank you for your feedback on the performance part 😇
So yes, I agree that it also depends on the complexity of the compositions. It is not the same to try to play a calmer, softer piece and something that is technically very demanding. Not the same at all. And I also like the comparison with athletes. When you can not play or do a sport anymore, as your body is not that flexible and perfect, you become a coach or a teacher :D hahahh