I'm somewhere in the middle between Milwaukee and Makita. I use Makita for my impact drivers, drills, saws, oscillating tools, grinders, etc and they are my most commonly used tools. With that said, I also have a pretty extensive set of Milwaukee M28, M18 and M12 tools as there are quite a few tools, especially in the electrical trade, that Makita just doesn't have or are better suited for the trade then Makita.
By far, my impact drivers and 1/2" drills take the most abuse and I'm pretty happy if I get 2~3 years out of them, but I still have all of the batteries I got when I returned to the trades almost a decade ago.
Battery upkeep is by far the most critical part of maintaining the life of my tools. I routinely cycle batteries, make sure I always charge them at the end of the day, always store them overnight in a heated environment and NEVER let my batteries get stored longer term without a full charge.
Lithium batteries can put up with a LOT of abuse, but extreme cold and letting batteries drain below their charge threshold is a sure way to kill them quickly.
Just my two cents.