I've never tested it, but I think it is safe to assume that their helmets will never run out of oxygen, just like their shields never run out of energy.has anyone tested if the oxygen in their helmets runs out if you activate it and wait ~20 mins in your ship?
Besides, I'm not waiting 20 minutes to test that, either. Especially not when it takes me about five hours to do a batch of 10 or so missions for BGS/Odyssey grind.