i personally think that using a burned disc that is of questionable quality can overwork the laser in several re-read attempts and hasten the wear on it. however, if you use a high quality burn (slow speed, high quality DVD+R media) it should be just fine. i've left a very low quality disc in the MK4 for several years without problems. but in helping others with their MK4 upgrades, I've seen some units that will no longer read or have trouble reading the low quality burns. but once i make an image of the DVD and re-burn it to high quality media, the unit took it just fine. in light of that, even though I hadn't seen any problems, i switched my disc to a high quality one and leave it in the MK4 at all times.