For me the automatic PayLoad mode used 0x60, while I was playing, and like that the CPU was around ~62C.
It's highly possible that if it changes the fan speeds only based on the CPU, as you said my GPU become too hot suddenly, while playing MGS4, and as it didn't notice it the fan speed didn't increase any more. Possibly it would be a nice idea to implement the same thing for the GPU into Iris manager, so when there's a problem like this it could (maybe) help.
By the way, my PS3 was repaired from a YLOD almost 2 years ago, since then it didn't have any problems, and I started to use Iris Manager first when I've started playing MGS4, I was happy how cool my PS3 is, and hoped there won't be any problems, and the second day this happened. Can there be any relations about the faster fan speed to the problem, or is it a total coincidence?
My PS3 will be reballed next week, am I better off if I start to use it now already with Iris Manager, and use it always, so it keeps the PS3 more cool? Also, can I expect a longer life for it like that?