I have instance for couple of years. No issues for now. Never had a feeling it's going to fall apart. I host it via docker image, pull new version from time to time and that's mostly it.

Only two problems I can think of: it's bit slow - even our company instance which has reasonable resources could be bit faster. Also they could use a better UI designer.

None of it is major problem for me. As self-hosted Dropbox/calendar/cospend it's perfectly fine.