That's why I roll all LED, all the time. I never have to worry. I just change the batteries every Christmas so they don't go stale. Never really had one go dead on me.
That's after years of batteries being dead every time I grabbed a light. As soon as the first LED flashlight entered the consumer market, I bought one. I've still got it, and I've only changed the batteries three times. They have never actually died. My current favorite is my Streamlight LED Tasklight, 3AA. It's bright as all hell, and I've got the same reliability.
I'm going to try one of the newer Pelicans soon, just for kicks.
Edit: I've actually used the Streamlight as a vehicle's headlight before.
Cheers,
Kennith