I feel like we explored this topic recently, though there's one angle I haven't thought of:
I have never seen anyone spin three of a kind Mystery Meat. Maybe one or two and jokers to fill out, but never all the same. If that's true, if the players exhaust all of those questions and the show doesn't want to do a jump cut and have Jack/Jim/Bill explain why new questions have magically appeared, there is always an out-draw for the player--either another category to choose or a joker that can be converted into one of the other four categories.