I know quite a few helicopter pilots who are just afraid to fly higher than 500ft. I personally have worked my way up (yes, I am afraid of heights). Been there, done that, 14'000ft in a R22. Looking down between my feet was scary but one gets used to it. In Alaska, everybody flies at 500ft, therefore I decided flying at 3000 feet is much saver and you get a better view.
3) Less distance to fall if something goes catastrophically wrong (tail rotor failure, blade delamination, fire, tail boom comes off, etc etc, not just an engine failure-autoration)
Well, still hurts and you are dead anyway. No, that isn't a reason.
5) Less time in auto-rotation means less chance of the blade stall while you come down? A momentary lapse of attention to RPM in an auto rotation might be more likely if it takes several minutes
It is pretty much impossible to stall the rotor in an autorotation, once you pushed the collective down. After all it windmills. Overspeed is more likely but who cares about the blades as long as they bring you down.
6) in Robinsons anyway, you don't lean the fuel mixture in flight so I guess the fuel consumption advantage is not there as in a fixed wing where mixtures are leaned at high altitudes
Also, been there, done that. You can lean an R22. It makes sense when you work high up. Just land somewhere, lean, take off again and don't do it in flight. Never, ever, ever. And don't forget to PUSH the mixture all the way in, when you come down again.
Apart from long ferry flights, the fuel consumption would not change a lot anyway but performance changes quite a bit.