'Till it quits. I have 2 old ones from latter part of '09 that work great, one of which is on my desk at work and gets used all day everyday. I have one of the newer ones in the truck and I had it replaced after a couple of days, but the replacement is fine... so far. As long as the cable isn't damaged and the switch (auto or manual) funtions, they should last a good while. I keep mine situated where there's not much movement so as not to twist or bend the cable around which can sever the the wires.