I always wanted to make feature flags system where each FF must declare an expiration date max 1 year in the future and start failing CI beyond that date to force someone to reevaluate and clean up.

It's just too easy to keep adding new feature flags and never removing them. Until one day the FF backend goes down and you have 300 FFs all evaluate to false.

We've done that at a few places I've been at - it's tricky because if the failure is too short its just annoying toil, but if it's too long there's risk of losing context and having to remember what the heck we were thinking.

Overall it's still net positive for me in certain cases of enforcing things to be temporary, or at least revisited.