It’s time to change all your batteries again - and not only in photo gear.
   Make New Year’s the day you change all nonrechargeable batteries you have - and you won’t suddenly find yourself with something that doesn’t work when you need it most.  Clocks, flashlights, radios (including scanners and memory backup batteries - and, of course, speedlites and ring lights for photos.  And anything else.
   I strongly suggest Ray-O-Vac alkaline batteries; I’ve never had one leak - nor go dead in less than a year without use.  Lowe’s sells them cheap in bulk packs of 36 for the ultra-common “AA” variant - and also “AAA” ones.   And - needless to say - use only alkaline batteries; anything else just won’t run as long in use.
   For speedlites, also change them in June - as they are out in hot and freezing cars often.  And I’ve never had a bad experience changing those every six months that way.
   And replace any battery when you use it.  Let your client pay if it’s in photo equipment.  That way, you always start any job with fresh batteries.
   It’s easy to remember when to change batteries this way.

 

Don’t forget the one “AA” battery your small tactical flashlight uses!
Flashlight about $26 at Batteries Plus.