I have 5 Aimpoints (M2/ML2's) I bought back when they were the state of the art almost 20 years ago now. They are old school now, and only have a battery life of about a year, but have never failed, and still work great.
I just changed out the batteries for the year this afternoon. They run 24/7/365, and I change them at the time change in the fall. I have never found one dead yet either.
Two of them are on guns that get used a couple of times each month and have quite a few rounds through them (both guns and dots). The guns arent babied and have been banged around a good bit, and Ive never had any zero or sight issues.
The reason I went with Aimpoint was, I tried a number of the "cheaper" but still big name dots of the time (Bushnell, Tasco, etc) and had a lot of trouble with them working, holding up to being shot a lot, and battery life was dismal. Seemed every time I got them out of the safe, Id forgot to turn the dot off, and the battery was dead, again.
If I had back the money I wasted on those sights, Id have a couple of more Aimpoints and maybe a mount or two. Buy once, cry once.
I really couldn't afford buying them when I did, but I figured out a way to get it done, and Im glad I did. I havent regretted the decision in the least.
By now, they are starting to zero out and I think right now, they are working out to have cost me something like $20 a year at this point.