Reputation "Spread" override after x days?

[Greebo]

This question came up in my forums today and it seemed like a really good idea.

Ok - reputation has an option to force you to spread the love around a bit before going back to a particular poster. Great - prevents people from simply bumping up their buddies ad infinitum.

But..

Would it be possible to ignore the "spread limit" if a certain amount of time has passed since the last time the person giving reputation gave it to the person receiving it?

Example: Bill really liked Joe's post 3 months ago and gave a positive hit.

Bill hasn't given out much reputation since then.

Today Joe posted something else Bill really liked. Bill can't give reputation because he hasn't spread it out - but with this modification, since the last rep hit was given to Joe 90 days ago, Bill can go ahead and give it.

How hard would it be?