There's a belief in certain corners of the gaming community (and maybe other communities that deal with optical discs) that if the disc drive's laser has to "try hard" to read a disc it will eventually "burn out". Not sure if this is backed up by any actual data or facts - it sounds plausible to me that a laser might dynamically adjust its power level as needed, and that over time that might be bad for it; but it also sounds a bit like people might be anthropomorphizing the laser or something.