i only have one EDC light, my Fenix L0p, and it has been riding with me for about a year and a half now, and when i just tested it, it still worked
everything else get rotated, my old grey 6p lasted nearly 4 years on my duty belt and still works,it just lives in a drawer now, i changed jobs
my magcharger now lives in my car as a percussive persuasion tool and street number finding light
my 2 year old SF U2 still works, along with its predecessor, the L4 (now 3 and a half years old.
my T4 did a year on my duty belt, then my fiancee pinched it for hers, and now i have i have it back, and it still seems to work
my Streamlight strion which is my current edc, still works too
oh, and i will be ordering a Novatac later tonight, hopefully it lives a long life as an EDC light too
EDIT - just ordered along with a rechargeable 123, and 18650 for the U2 and 2x 17670s for my L4 and Inova T3