11 years seems to be the limit. The CW has canceled 7th Heaven.
The news was reported by Kristin from E! Online. She left the following brief note on her blog site:
Folks, I just heard that after an astonishing 11 seasons, the Camdens are leaving us: 7th Heaven has been canceled by the CW.
No official comment yet, but I’m told that the producers, cast and crew were informed by the network today. It’s a done deal.
Until there is official confirmation, please treat this news as rumor.