Batteries last 5 years in very dry packages under 90 degrees Fahrenheit, but this might be a nice place to mention new coats for batteries; PD&D Magazine mentions them as cutting the electrical damage bit out of the swallowed batteries risk. Then I would ask about the naivety of supercaps, now with catastrophic conversion -over- 110 degrees Celsius (or when ingested, I suppose.)
I would be much happier paying the same amount for something that looks like a AA battery and will last a few years.