Originally Posted by cyccommute

Sorry but I'm not buying that you can get 2 hours out of a "insulated" water bottle. Half an hour out of an uninsulated one I can agree with but the insulation of something like the Polar will only buy you about another half hour, if that. That may be enough for a 40 minute commute but I really doubt that you can get 2 hours out of an insulted bottle. The other part of the problem is the thermal mass of the water itself. There just isn't much there to start with. If you are consuming the water as you ride, the thermal mass decreases and the amount of heat that it takes to raise the temperature decreases as well.