The steady headwind is all it needs to continue to create lift and therefore fly.
The determining factor here is how long the pilot can continue to fly the aircraft as it's groundspeed takes it out of visual range.
A glider in a steady headwind capable of keeping it aloft, while being controlled in a manner that prevents it from turning downwind or otherwise crashing, can stay aloft until it's receiver battery dies and that control is lost.
It's essentially a kite without a string, and kits don't need motors. They also generally don't have airfoils. All they need is angle-of-attack and a headwind and they can stay there indefinitely.