Shelf life is not the problem. My light is made by surefire it uses 3 cr123 battries. they last aprox. 20 min. of on-time. the stated shelf life is 10 yrs.
they are expensive about the best deal i have found is from surefire you get 12 battries for $15.00. at wally world they run $3+ each. some tac light are using led's instead of a bulb, there on- time should be longer,but the light out put may be less.
I made the mistake of buying a surefire for an everyday flashlight. The battery lasted me maybe a month. The shelf life is 10 years but the actual run time is about 10 minutes. I never noticed the bulb getting any dimmer, it just quit. so I bought a new bub thinking I had dropped or it had burnt out. Wrong, it was the battery. My everyday light is now a streamlight twintask. I haven't used it a lot yet but I do expect the battery time to be much longer.
The low-voltage warning/signs will be a function of your particular light. Normal lights like the M3 will get dimmer as they batteries die. Lights with electronically regulated voltage, like some of the Surefire lines will get dimmer or just stop working.
Each tac light should give an estimated time that it will work before lumens drop off. For the M3, i believe the run time is estimated at 1 hour. Same for the Surefire X200. This data should be published my the mfgr.
With a high-power tactical light, expect to replace the batteries after 1 hour total running time. You don't want to be cought with a dim light thats purpose is to blind someone.
Batteries are cheap compared to your life. Keep a spare set and switch them out if you think the light is getting dim.
I have a Streamlight twin task for a bump in the night light. It uses two of the lithium photo batteries. When the voltage is too low to power the conventional bulb, the three LEDs will still provide usable light. It isn't a true tactical light, but it serves the purpose. I just make a point of clicking thru the LED setting before I turn it off, that way the high beam comes on when it is first turned on instead of the dimmer LED light. (For anyone not familiar with it, it has a push button that cycles thru bright white, off, blue-white LED, off again and then back to white.) I really like knowing that I have a couple of nights worth of light if I need it, or an hour or two of high intensity light.
I began with Streamlight SL20X, then got a Stinger, and I recently bought the best little tac light, the Strion. I've owned the same SL20X for 15 years, and the Stinger for about 5. I bought the Strion last year. GREAT lights. I highly recommend Streamlights over Maglights and I would depend my life on a Streamlight.
For those who have not seen any of the above three lights, you should definitely try to get your hands on one to see the lighter weight, small size, and BRIGHT light.
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