I have about 20 of them and I think maybe one has gone bad. I love them. I don't use them during the summer. Start using them in the fall and thru the winter. I always use the timers.
One thing I have found is the ones that take C or D batteries last much longer. I do have some votive size that take AA batteries and they go out sooner than the C.
Also, after I don't use them starting in the spring, I remove the batteries. I keep them separate from the new batteries and put them back in when fall starts. That way if there's any life left in them, I get the full use.