1 year update:
Laser has been getting dim recently and turning off by itself. Replaced the batteries and all seems fine. Range trip this weekend to confirm.
It's hard to say how much time it actually spent on in the past year to evaluate the battery life claim of 5 hours in constant mode, but I'd guess it's pretty close. I've spent quite a bit of time practicing turning it on during my draw, and used it at the range as well.
The original batteries in my Beretta guide rod laser are still good years later, to give some kind of comparison.