The irritation that comes with a leaf that sends roots through your entire propagation tray but never puts out new vegetative growth. Times up! You’re evicted. It’s fine to start making room for the spring seed trays. You had all winter to get your act together.
Echevaria Nodulosa are notorious for this for me. I’ve heard some people swear that you can’t propagate then from leaves, and I have pictures to prove you can, it’s just going to take a lot of attempts and rejects like this guy.