Ni-Mh should be charged with 1C charge current, that means 1 x the the capacity of the cells. With a 700mAh battery you should charge at 700mA charge rate. Mst Ni-Mh batteries can handle 2C though and that's how I charge my 700mAh battery (2C = 1,4A charge rate).

At 2C a completely drained battery will take 30 minutes to charge, but since they are never completely drained it takes a little less time than that. I usually charge for 20 minutes at 2C. If I have to wait a while to fly I charge at a lower current, for example if I charge while I work and fly in the breaks.