# of cores + endurance rules..
Avoid high end ocing unless you have a large budget for hardware replacements.
(the story of the tortes vs hare)
A lot of XS WCG people (me expecially) did a lot of hardware replacements to hold up high overclocking while being loaded. If your not the type that can RMA stuff fast, or its your main machine, down the overclock so she's not tiptoed all the time.
Oh and when your cruncher does suffer from down time.. (unfortunate event but will happen)
1. most likely its your RAM
2. it then falls on the board.
3. the cpu is usually the last to die, unless your pushing 1.5vcore + on WCG. :P