I think it's a good practice before doing any OC, just run some tests like memtest, prime95 etc on stock settings, just to check temperature etc to make sure the contacts good. I remember one time I talked to this kid who actually put together his rig for like 6 months already. And is complaining that whenever he runs anything intensive, it BSODs.
I went to his house, fired up prime95, it immediately BSOD under a minute. then i tried second time w/ system monitor on, sure enough his temp quickly climbed close to 100C then the cpu shuts down for self preservation.
Opened up his rig, and u guess it, the huge TRUE he got was dangling off the CPU. no contact. amazingly he's been running this way 24/7 for over 6months!! I guess he mostly do browser and IM on it, never games or anything intensive. and he doesn't do a minute of testing either.
so from then on, even for myself, I just run memtest and prime for 20-30m using stock only just to make sure contacts good.