The Q9550 is a nice chip. I just picked one up recently too. Your temps look very good. I'd suggest using Intel Burn Test for stability testing too. It'll put even more stress on the chip and let you know if it's stable within minutes of testing, not hours like Prime95. But of course you should use both. My chip does 3.8Ghz @ 1.216 vcore on a TRUE.
Im also using OCCT for my stress test. Never crashed for the momment. Completely stable as far as ive used it ATM.....
I dont know if ill aim 4.0 for my 24/7 ATM. I really love my bios setting with thes 3.65ghz. With such low V on the NB and other this MOBO+CPU+RAM could run 24/7 for ages ... But the is going to be a "bad" computer in ages .... Thats the reason that make me lean on the 4.0 24/7 ... BTW its already VERY nice !
Just ran a 10 pass ITB.... PASSED. Your right, its harder on the TEMP. LOAD with ITB : (highest) 56-57-60-60 vs Prime 48-52 avg