I carry at least four lights when on duty (firefighter): A UK4AA Xenon and UK4AA eLED in my firejacket, either of which will attach to the Gallet firehelmet mount. I keep a Surefire G2 in my helmet bag for when I need a little more throw.
I keep a light in a pouch on my stationwear, rotating between:
Opalec MiniMag
Inova X5T
BB400 Q3L/Kroll MiniMag
Nuwai QIII
Surefire E2E/KL4
Off duty I always have an Arc AAA in my key pouch and will take another light when I go out at night, one of the lights from the rotation above.
You can't have too many lights!!