Two years on a MagicShine 802 with great battery life and no problems ($70). I just bought a MagicShine 872 two months ago ($140) and have been happy so far. Only complaint, it took a month to get here on the slow boat from china.
I did buy a blinky 1 watt bar mount led light for $5 a year ago. Didn't think it would last, it didn't.