[BrianG]

If you want long runtimes, then a lower kv motor is probably a better choice. Lower kv means more turns (windings) which means less current and better runtimes. They generally have more torque so you can gear up (within reason) if you need to go faster. And yes, lipos would be a wise choice - they are lighter so there is less dead weight for the motor to pull around than NiMHs. At an estimate; with 6,000mAh lipos, you should be able get about 30 minutes, 8,000mAh to be safe.