In these cases wouldn't it have been to work on it slowly as a "side project" outside of the team normal priorities? I always tell my team if they can fit it in and not hinder the current sprint by all means go ahead and do it on the side.
I know this goes against the normal and people want to attach "right now " value (hours it took reflected on check) but going beyond the call can also give you leverage when your yearly review comes up for example.