what about the heat of the laser contacting fingerprint oil?
As for system overheating, if you know how much dust can enter a computer after a few months, I would figure the DC is also vulnerable, and that enough dust in a fan will hinder the fan. My Gamecube came with the fan slightly jammed, so the fan wouldn't run at tpo speed, thus my system reset after 20 minutes of gameplay (within 1 if it had just reset). After opening the fan and resituating it, it worked fine for long periods of time. I'm sure the DC is similar.