Seinfeld is arguably the greatest sitcom, and also arguably the greatest television show of all time. If creating arguably the best thing of a thing is not success then what is?
In HBO's Talking Funny [1] (from 2011) there's a discussion (around 1:00–2:00), where it's pretty clear how his habbit of replacing old material in the act is far more infrequent and little-by-little compared to the other comedians around the table, who generally throw away their entire hour almost every year after a special.