It depends on the show. I can watch 20 episodes of I Love Lucy but can watch only 4-5 episodes of The Drew Carey Show.

It depends on the show, but it also depends on the frequency. If it's just one or two episodes every night I could probably stand it for a few weeks, maybe months. A long time ago (5 years ago) MeTV had about 7 different sitcoms in primetime every weeknight. Since that was just one episode each on every night, I never got burnt-out on the shows. I wish they would do that again.