With the motor that came with, I'm sure that's right. If you change your motor, it will change the run time on your batteries. Basically, the faster (more current draw), the faster the batteries will die. A low turn, high power mod motor will go through a set of batteries in about 6 minutes plus or minus (assuming your batteries are about 3300 capacity), so you are right. That of course is also dependent on capacity of the batteries. The big number on most rechargeable batteries referrs to the capacity. Most NMH batteries today are anywhere from 1500 - 3300, and you guessed it, 1500 will run about half the time of 3000. This is an oversimplification, but you get the general idea.
RC Car Action Editor and Photographer