Originally posted by: Furen
Electromigration affects everything that has a current through it but it really doesnt make a difference when metal moves, cracks or warps (that is what electromigration is) when you have a huge solid piece of metal conducting. Now, when you have wires that are nanometers wide, even thinner and only nanometers apart, then you start having problems. Electromigration is related to the current (not tension) density on the conductor and the heat (<- which is DIRECTLY related to the tension). Like Duvie said, it's more important to think about the temperature of the different hotspots. Even if you have insane cooling, it is not applied directly to the metal conductors, so you are still limited by all the thermal conductivity of the different materials (silicon, heat spreader, thermal paste, etc). You are correct, however, gate-oxide degradation is directly related to the electric field across the gate dielectric.
Edit:
Paintball: Now, to answer your question 😀. Most people dont recommend you going over 1.55v because (if I remember my formulas correctly) at 1.55 (from 1.35) you shave off about 32% of a CPU's MEAN life--so this means your cpu will supposedly only last you around 13.5 years from the original 20ish year rating. This, of course, is just an estimate, some cpus deteriorate much faster due to different opeating conditions and some take even longer.
NOTE that I oversimplied everything, there are lots of different things that affect a cpu's lifespan, but voltage is one of the important ones, and so is heat.
