However, to me, it does make sense that a power supply ran <100% would last longer than a power supply ran at 100%.

Absolutely. I think the part that is confusing to everyone, is a 750W PSU registering 750W on a Kill-A-Watt is actually only outputting approximately 637W (given say a 85% efficiency rating at that higher draw). To run it at the full 750W output, you would see about 930W on the kill-a-watt (assuming it only runs at a decreased 80% efficiency at max output).

check out jonnyguru.com

he is pretty much the guy with the numbers.

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=523http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story3&reid=523http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story4&reid=523above is a review of a corsair hx 1200 plat.

it has a 100 amp 12 volt rail

at hot and cold box tests.

92 amp is 89% hot and 89.4% cold. since we run 24.7 just look at hot numbers

70 amp is 90% hot and 90.6% cold.

46 amp is 92% hot and 91.8% cold.

he has numbers for hundreds of psu's

I try to pull 70% on my psu's so 1200 watt dc = 90.5 % efficient or 1200/.905 = 1326 max x 70% = 928.2 watts at the kwatt meter

look at 1200 x 80% and you get 960 watts

very close to the same 960 and 928.2

if the psu was 87.5% eff at a 70% dc load you get

1200/.875 =1371.4285 x .7 = 959.999

which is 960 = 960

So a 1200 watt psu on a 70% dc load with 87.5% eff is the exact same as 80% of 1200 or 960 = 960

so both people would be exactly correct some of the time.