Changing batteries?

[Irving]

One method I've seen people use is to change out batteries on lights and optics at Daylight Savings Time, along with changing the batteries in their house's smoke detectors.

With how much Surefire products cost, they should send out new batteries to all their customers every 6 months like my homeowner's carrier does for my smoke dectors.

[MrPrena]

As for OP's question, I haven't yet changed my weaponlight CR123 batteries for years, and it works great.
It is really difficult to predict when the batteries would go dead, because usages and capacities of batteries are all different.
Most frequent used flashlight uses rechargeable batteries, and my backup batteries are non-rechargeable (longer shelf-life).

[Rumline]

With how much Surefire products cost, they should send out new batteries to all their customers every 6 months like my homeowner's carrier does for my smoke dectors.

Crimson Trace does this once per year for their laser sights. You have to go online and request it though. Still, a nice touch.