Question about upping voltage. R9-390

Hey, so I've been reading online about overvolting, as my current speeds of 1135/1600 wasn't quite stable. Most websites say the downside of overvolting is that it errodes the electronics quicker. My issue however is this:

Is the heat the only issue playing a role in this situation? Or does the voltage also cause some decay directly even if heat isn't an issue?

I'm planning on keeping this gpu for 5+ years, and am wondering how much an impact +20mv can do.

im really sorry if I broke any rules, I checked the side bar on alien blue and didn't see anything rule wise.