Most of my night rides last about 90 minutes. I run my Shiningbeam MC-E on medium and it is good for a full ride and more. I'll click to high beam if I need to flash an oncoming vehicle or if I want to look at something off to the side of the road.
I have a $10 DealExtreme flashlight that I converted to run straight off the battery, bypassing the circuitboard. I thought about mounting it on my handlebars to use as a superbrite auxiliary light but I just haven't got around to doing that. That one only gets used for short bursts because of heat and battery drain. I've been using that light for a couple of years and haven't had any problems with it.