Focus on the stall current which is the maximum current the motor will consume under its maximum load. That's 1A (or 1000mA). To drive two motors at full power for one hour you need 2Ah (2 amp-hours) or 2000mAh. An AA, rechargeable, NiMh battery just happens to be around 2000mAh.
You can use a battery greater than 6V with your motors if you just limit the current to them; of course this is easily done with a motor shield by simply not running them at max power. If you're not sure if you're running them with too much power just feel them and see how hot they are; if they're hot then supply less power.