I got a i7-2600k and i want to overclock it. i got a h100 cooler and the idle temp is 35C and at full load its 50C. i want the cpu to last about 5 years. will overclocking it to 4.0-4.5GHz make it last for more than 5 years? and if so, what voltage should i use?
Adding voltage always decreases the lifespan of components, but just stay below below 1.4V and you should be good. For 4.5, you really shouldn't need much over 1.33V, if that. At that voltage, I'd say ~5 years is almost a definite, IMO.
A properly cooled processor running at stock voltages and clock speeds will last far longer than the life span of the computer, possibly 10 years or more. The factors most likely to reduce the life span are heat and voltage. Clock speed increases shouldn't decrease the life span directly. As long as you keep the CPU cool (~65C at maximum load) and keep the voltages within spec (under ~1.35v) then lifespan shouldn't be reduced significantly. If you can keep your voltages low (~1.3v) and your temps are low, then your CPU should be able to last at least 5 years.
As an aside, the 35C idle temp for your CPU does seem a bit high. I have a i5-750 on an air cooler and it idles at ~29C. Then again I may be wrong, so if anyone has experience with an H100 feel free to chime in.