When do you actually go back and remove old feature flags from your codebase?

Wrapping every new release behind a feature flag makes rollouts much safer and lets you kill broken code in seconds.

The problem shows up six months later when the codebase is full of nested conditional checks for features that have been live to everyone for ages. Nobody wants to touch old flag logic in case a forgotten edge case breaks.

How does your team enforce flag cleanup without turning it into a massive quarterly chore?