Well the headline is 2 years, but the detailed explanation is that you get around 40,000 seconds of recording time, with normal use. They describe normal use as up to 10 x 5 second motion clips, or viewing events, per day, which does indeed come out at around 2 years. I imagine it would be significant if the events were at night, but I don’t think they mention that. That’s less than a minute per day allowed, to hit that 2 year life. In a high traffic area, with longer record times chosen, it’s very easy to see how you could burn through the batteries extremely quickly.
For one camera of mine, I’m hoping for really long battery life, because I get only one event per week, on average, so it will be interesting to see if that leads to even longer life. The batteries have a very long shelf life, and the low power mode is very low, so I’m hoping I might get 5 years. Less than 2 would be disappointing, 2 years will be satisfactory and 5 years will be fantastic. Only time will tell for me.