There is a setting — post undo action window mins. This is described as “Number of minutes users are allowed to undo recent actions on a post (like, flag, etc).”
In many cases, setting values to “0” means no limit. I’m not sure that’s the case here — if it isn’t, you could set a ridiculously high numbered to effectively be forever.
But this doesn’t change just that. It’d be nice if the documentation text were a little less vague on what the impact might be.