Wingbone,
The answer is extra batteries, in the 123's lights it can get quite expensive to exchange 3 batteries every 20 minutes for the 200 lumens output.

You probably will have noticed that the RECHARGEABLE Bear Cub will give you one hour and a half of run time at 220 lumens, the lightweight Lithium Ion computer batteries that it uses can be carried as extras in a pocket for extra run time. They recharge in 3 1/2 hours in the Fast charger that comes with the light.

white bear