Not only ditto what Jack said, but you're at risk for something to happen breeding ANY bitch of age. There are a number of things that can go wrong, and age has nothing to do with many of those things. There's no reason to stop breeding a bitch at 8 years old unless you simply want to. If the dog has been kept healthy her entire life, and you want to breed her again at 9, you're not going to because someone told you that 8 was too old? I laugh all the time when someone tells me their female is too old to have pups, only to find out they're anywhere from 7-9 years old.

That's just silly.