I've been running my 4 module version Avalons at 350mhz using the stock PSU. Is this bad?

I have had 7 Avalons at 350mhz running on the stock PSU for about a week. I did have to replace one PSU, but otherwise they seem to be running fine.

In my previous experience when a PSU goes bad, the whole machine just shuts off, after replacing the power supply everything is good to go and no extra harm was done.

Am I taking a large gamble of the PSUs failing and potentially harming the equipment?

I read in the Batch 3 thread that a four module Avalon @ 350mhz runs at 930 Watts at the wall. I think the Avalons only ship with 850w PSUs. So obviously what I'm doing is probably risky, I'm just wondering how risky??