I was recently asked by a young counter staffer who could not make change without the cash register whether I wanted to buy an extended warranty... on a pack of batteries.
You should have gotten the warranty and then gone back in a month and asked for a warranty replacement "These are defective, I put them in my flashlight and they worked fine for a few weeks, then just stopped working."
The anecdote from cf100clunk is apical and worth spreading (and I do not believe represents a "single isolated case"), but the follow-up J. suggests is not impossible:
a story is known (not verified) of someone who insured a box of precious cigars, but in time smoked them, then requested payment from the insurance - presumably thinking "if one is fool enough to cover consumables, then has to follow consequently": the insurance company sued the insurer for arson.