I stopped watching about a decade ago, and it was already getting long in the teeth then. The slow transition from goofball comedy to sooper serious plot put me off, as well as the shift from machinima to Monty's CGI wankfests. I forget which season premiere it was where it just started straight off with bad CGI instead of machinima, maybe for the entire episode, and I decided I'd had enough. Didn't watch any more after that, and that's also pretty much when I stopped following anything RT-related.
It's been years since I watched any RvB, but seasons 1-5 probably hold up more or less, seasons 6-8 are okay but kind of mixed, and everything after that I don't even remember if I watched it or not.