If the interim champ defends for a second time, he becomes the champ. Any cutoffs based on time invite unfair results.
Remember, we want the guy who has the title to be thought of as the legit best guy in the division.
If we did a year cutoff, GSP would have lost his belt and someone else would have it. That would just be wrong.
I AM NOT IN FAVOR OF PAPER BELTS.
If the interim champ defends twice, his belt seems legit enough to call it the real thing. But at the end of the day, even that is a little bit of a paper belt.
If we're stripping champs every time they're sidelined for a year whether or not it's their fault (e.g. their opponent gets hurt, fight is postponed a few months, then they get hurt and are out for 8 months, = loss of belt?) then we're going to have MAJOR paper champ problems.