I live in Arizona and it is well over 100F all summer long. To make matters worse Im upstairs and it is hot as hell up here even with AC. Should I slow things down a bit to prevent to much heat on the computer? Right Now Im at about 4.0Ghz coming from 4.5Ghz.

Whats the temps at 4.5?

Last time I was downstairs and it was around 38C idle.

Thats fine. What about load? So long as it doesn't go above 80-90's you'll be fine. If its 60's-70's your perfectly okay

how much will oc cut back the life of my computer? Downstairs underload it was never above 65C

Thats fine. Perfectly okay. What CPU is it?

Intel i5-2500k. However what concerns me is the voltage that is required to power 4.5ghz. My chip requires 1.41-144v for stability. below that it will bsod.

Ouch. Looks like you didnt get one of the better batches. But yes, 65 at 4.5 is fine

will that shorten the lifespan a lot

Nah. I doubt it. These sandy bridges are made for overclocking. Maybe a little shortening (a couple of months) but nothing drastic. Only if you start over volting. Then the lifespan will take a hit

and overvolting for a sandy bridge I believe is like 1.5v and above

1.45 is what most recommend as the max before you push it too far. But yes. Damage could occur at 1.5

Intel i5-2500k. However what concerns me is the voltage that is required to power 4.5ghz. My chip requires 1.41-144v for stability. below that it will bsod.

Is that BIOS voltage or monitored voltage in Windows? Idle or full load voltage?

Get a small fan, take the side cover off, and blow air over MB. If you are worried about dust, dirt, critters, then cover the side with a small piece of fiberglass window screening material from your local hardware store.

Bios it I had set in fixed mode at 1.45 and it never exceed that underload.