I use the Lincoln Power Luber, just the regular 12v, I know they make a bigger one. I have 2 batteries and always keep one on charge. I try to remember to swap the fresh battery from the charger to the gun before I use it or take it with me to a job. Seems to last a long time. I'll put it this way, I seem to change grease cartridges a whole lot more than batteries.
I about wanted to cry shelling out that much coin for a d@mn grease gun, but after having one I'll never go back. You gotta be a three armed monkey to use a lever gun and a pistol-grip is the fast-lane to getting arthritis in your fingers.
My buddy is a dairy farmer and has a Lincoln too. He had to get a new one last year finally. His old one was about 6 years old and had been run over with equipment several times and left out in the rain quite a few times and just wouldn't quit. The plastic housing was cracked and had pieces missing for awhile and it still worked. It's final demise was taking a spill off of a tractor it was left on going up the road. It may have still worked, but he was never able to find it, lol. Needless to say, they seem pretty durable from what I have seen.