>>My photon II has the same battery for the past 3 years and I use it a lot. I don't understand.<<

Ditto. I carried a Photon 2 in my keycase for years, still haven't replaced the battery. I carried a first-generation Photon 3 for perhaps a year, no problems, and am about a month into the second-generation Photon 3 (with SOS), no problems yet.

Obviosly, my preference is for the Photon 3, mostly because of weight. Current model is a Stealth version, mostly just to protect the LED from abrasion, but it never really seemed to be a problem with earlier versions. If I had my choice, I'd go with green, red, or orange, for the better battery life, but this one is white- it's what was available at the time.

Depending on your circumstances, the new SOS feature may be mostly irrelevant or highly desirable. If you can see a reasonable scenario for using it (not hard if, say, you spend time on the water), it beats the heck out of spending hours flashing S O S by hand, while not being free to do anything else about your situation. I've bought 4 so far.