The manufacturer does not state the battery life of the Hawk Gazer FLG-21 LED Flashlight/Green Laser Combos. I recommend contacting the manufacturer for that information.
The manufacturer does not state the recoil rating of the Hawk Gazer FLG-21 LED Flashlight/Green Laser Combo. It should be fine on a .308 rifle but I recommend contacting the manufacturer to confirm.
This means the Hawk Gazer FLG-21 LED Flashlight/Green Laser can be activated with the laser by itself, the light by itself, or both the light and laser at the same time.
The Hawk Gazer FLG-21 LED Flashlight/Green Laser Combo can be mounted directly behind your front sight post and will allow the light and laser to overhang on each side of your rifle with an unobstructed view. The included pressure switch does not have a specific way to be mounted to your rifle. You can use double sided Velcro, 3M tape, zip ties, or any other method that allows you to mount the switch in a comfortable secure location.