Consumer PSUs are not meant (not made for) to be run at 70-100% capacity 24/7. That said it doesn't mean they won't. I try not to do that. For example, for my 900 watt systems I generally use 2x 750 watt power supplies.
Also, at 90% capacity you will use more electricity as they start to lose efficiency when you pass 50-70% <- I admit I don't know the exact number.
I highly recommend you (and everyone) install a smoke detector close to their rigs just in case anything goes wrong.
Every atx I run at 80 % or higher dies young two or three years not five or seven or ten years like their warranties are.