It's fairly possible that a heavily overclocked - but well cooled CPU is going to last longer than a poorly cooled CPU stuck in a box full of dust.
Extreme voltages do have an affect though, something about electron migration or something. But it's theoretical, not proven.
I have never, ever, seen a post along the lines of "My A64 finally gave up the ghost, I guess it didn't like the 1.5V it's been getting for 2 years"
You can damage components by putting a stupid voltage through them, and you can burn chips by not fitting a cooler. There's videos of exploding CPUs going about, quite entertaining to watch. Although with IHS being standard it's less likely we'll see flying blobs of liquid metal.