while i think the Cosby show Show was getting bad by it Sixth Season With Olivia the show was not as good as it once was nobody was really funny(Even Cliff wasn't as funny as he was in the first several years) and the rating began to drop From season 6 through season 8.
so what i want to know how much longer could they have lasted?

The show would've gotten even worse had it gone on longer than it did.

They should have stopped when it came to adding Martin and Olivia. Instead, I wished they didn't add them and just move forward. But, if given the choice of move on with them or just quit, I vote QUIT. It was friggin' annoying seeing Olivia.

The show jumped the shark with all the cast additions. They should've thrown in the towel. The show was a mess towards the end, in my opinion.

I think they could have gotten one more season out of it. They were still in the top 30 during the 1991-1992 season. The show was getting old and jumped the shark several times and it still screamed 1980's when the 1990's hit.

I didn't care much for Olivia, but I'm among the few people, who actually liked Pam. But then, I didn't grow up with the show just being about the Huxtables, so that might be why I wasn't so bothered by the later seasons.

I think The Cosby Show would have gone 12 seasons

I would have loved to see Sondra as a teenager or Rudy as a teenager. So I would have liked more seasons, either from before it started or from after it ended.