This can be a problem with rechargeables too, if you're the kind of person (like me) who doesn't like to keep the built-in Li-Ion cells topped off to 100% all the time. So I'll often let my Dinotte Quad Red go for 8-12 hours before I plug it in for recharging, but at some point I assume the battery is going to have aged enough to start shutting down on me in that time.

More seriously, I've had some AA and AAA lights that would shut themselves off after an hour or two of bad roads, presumably because the battery would momentarily lose contact and the light would reset. Since most of these lights have a soft power switches, once the circuit de-energizes and loses state, the light has no way of knowing it was supposed to be on once the battery makes contact again. I've had problems with older Cateye, Planet Bike, and PDW lights, though I have a few newer Planet Bike blinkies and haven't noticed any issues, so maybe they figured it out finally.