Mark, lots of good points. I received my SOS light a few weeks ago, marked on the batteries the date, and installed them. Actually I wanted to put Lithiums in it. But after looking high and low, it doesn't appear any of the regular manufacturers make a lithium C cell. So I stuck Alkaline in it. However, I think I will check them every few months, as I've had batteries break down and leak acid out in the past. I still have my flares, but at least I can keep those a little longer now past the expiration date! Colby