So far as batteries are concerned, those coin cells in the Photon are expensive-
Note they need not be. Just buy them in about qty 10 over the Internet and you should be paying about $.60 for name brand CR2016s, or less for "generics" (pre shipping). Since they will keep 10 years on the shelf, no real downside. Check out
cheapbatteries.com. Isn't the Internet cool?! :-)
-john