Yes these temps are safe to OC, now you must remember that people love to blow smoke. I somehow doubt thatan i7 960 on air cool (the same setup as you even) could achieve 45C.
Here something that might convince you that I'm right. It's a few threads I gathered after a quick google search.http://www.tomshardware.com/forum/280887-28-temps-okayhttp://hardforum.com/showthread.php?p=1035417823
And to overclock, from my experience, as long as you stay within 90C it's acceptable. I usually thrive to get lower than 75C for longevity purposes, but I always WC which gives me a lot more to work with.