In the UK I'm watching nightly re-runs of the whole Seinfeld canon. At present they're running 1992 episodes. I've just watched one where there was a joke I'm sure they used twice, the only occasion I can remember it happening. Jerry is in his apartment, the phone rings and the guy on the phone tries to sell Jerry something and Jerry says "I can't talk now, but if you give me your home number I'll ring you back" The guy says "Er, we can't to that" "Oh" replies Jerry, "is that because you don't want people ringing you at home"? "That's right" says the salesman. "Well now you know how I feel" says Jerry.
I know I saw the same joke in a more recent show a couple of months ago.