Depends on how you ride, also. If you're flat out all the time, running super rich is fine.
My polini V1 race bike has 70+ hours of track time with klotz beanol at 20:1 and looks brand new, aside from a bit of burnt carbon on the piston.
I've run my cimatti Gran prix V1 polini on 20:1 klotz on the street (usually just using up my extra race mix) for hundreds of miles and it's still clean, never soft seized, and runs great (and smells nice, too.)
But I ride it flat out all the time. It's a 53mph bike and I hit that for extended periods of time, every ride.
Only thing I've had to do is run a hotter plug (B6 from B7) because it would foul out every other month.
But if you're the slow cruiser type that never does any maintenance, you're gonna get clogged up running it super rich.
At least that's my experience.
But the oil debate will continue on forever.