I realize that there is a love/hate relationship with installing an electronic item like a red dot on a pistol.
With regard to battery life, I have found the big issue is with the battery itself rather than the device.
We have no idea how long most batteries sit on the shelf. A typical 3 volt red dot battery will measure as high as 3.35 volts, and one that has been sitting a while can measure closer to 3.0 volts.
Clearly, longer life can be expected with a 3.3 ish volt battery than a 3.0 ish battery.
Before I swap mine out, I check it with a $10 DVOM and write the voltage and date on the battery with a sharpie. Personally, if it doesn’t check at a minimum 3.15 volts, I won’t use it.
This habit of checking and documenting takes no time, costs no money (assuming you own a DVOM) and I recommend incorporating it into your predetermined maintenance schedule.

You happen to have a link to the $10 DOVM?

I use this one. https://www.harborfreight.com/...ultimeter-63759.html
I have had it for years and works fine for simple stuff.

For a $10 DMM, look at the Aneng M108 or M118.

I paid $10 for my Amprobe PM60 but they are discontinued

Voltage is not sufficient to evaluate a battery. Several inexpensive DVOM offer a battery load test. Suggest you choose these DVOM for true eval.

Things have gotten expensive and the Harbor Freight DVOM in the link above is no more. They replaced it with a $20 model but Amazon still has deals on reasonably accurate offshore junk. Still $10 availability if you look.
https://www.amazon.com/ANENG-M...s%2C161&sr=8-11&th=1

While checking battery voltage alone is good, better still is a tester that applies a load to the battery while monitoring voltage. While this one doesn't give voltage, it rates the battery with a percentage of useful life remaining. Quick & easy, but at near $100, not cheap:

https://www.amazon.com/dp/B000...t_b_fed_asin_title_3

It probably only makes sense if you have a lot of batteries to test. Being in electronics field for the last 60+ years, I've almost as much test equipment as guns.

This message has been edited. Last edited by: bumper,