Initially I was told to keep using them for life. No one has suggested otherwise and I'm approaching the 5 year mark. Although my dentist did say about a year ago that I could cut back on the every night usage of the trays to a few times a week and just brush with the Prevident the other nights. I sometimes do this but it's more like 1 or 2 nights per week off the trays. That's mainly because my RO suggested I keep using them. I'm hoping to see her again for a checkup in January and will ask again. Guess I figure since it's no big thing and I really really really want to keep my teeth, what the hell!

(oh and like my compadre just above I've always taken good care of my teeth and had and have no problems that required any extractions or other dire methods back before I started treatment)