I've just been studying these perpetual motion machines:
https://www.youtube.com/watch?v=287qd4uI7-E.
Seems like the best approach would be to mount each crank to be stored on some kind of rotisserie apparatus powered by a perpetual motion machine (would probably need to be part of the totally balanced machine) to turn it continually without the use of any power for eternity and prevent sagging. Huh?