[nosmokewhereiam]

What if the drones didn't loiter in the air for 4 hours, but rather "hopped", resting on the ground and powering down.

Powered optical spools or really cool batteries or power line recharging as other wildcard guesses.

...or a ton of drones redeployed at intervals.

That's all the guesses, y'all are going to have to scrounge for more. I'm going with the "hopping or bounding" guess.