If they don't, they should be stripped of every belt they hold, not just the one whose mandatory is due. Give them one injury delay per career. Anything more gets them stripped. The champs only fighting once a year or less is killing the sport. It leads to most of the top contenders not fighting more than once a year themselves.
Heavyweights should fight once a year at most, with at least 8 months between 2 fights, for the sake of their health.
