What factor most likely determined how often a nomadic group moved?

The factor that is most likely determined how often a nomadic group moved is : Dwindling Food Supplies.

Nomadic relied on hunting - gathering activities to support their Group's living. If the source of food in their current area is diminished, they will move to a place with more source of food

The fact that had the most influence on nomadic group movement were dwindling food supplies because once they depleted or near-depleted an area of food sources, they were no longer able to sustain themselves there. When this would happen, they would have to relocate in order for them to enable their survival.