My I-C3 batteries usually last about 40 minutes before the power loss bugs me and I recharge. They could probably go over an hour, but I never wait that long...
Also, my stage-2 top speed motor didn't fit in my car right and would only go about 10 mph, whereas my drift motor goes about 12 and my drag motor goes about 15 (haven't even tried the road race motor). Check to make sure that the gears on your motor are fitting into the gears on your diff correctly.
Range sucks on mine too, my advice is to try standing on a chair
