I'd say if we didn't need stability I could go further, but that is a lie. I hit the wall already :|.
I'd say it has to be stable enough to run P95 for 5 or 10 minutes. That's what I run it on. As well as a SuperPI 1.5XS run at 1M and a HyperPI .99b run at 1M for <x> number of cores.