Jack, if you leave them turned on, not only will the batteries drain fairly soon, but the squeal of the microphone feedback will keep you up at night.
On the Gentex Wolf Ears, a flick of the finger on one toggle switch turns them all the way up to AMP, the desirable tactical setting.
With a little practice, this should take about two seconds.
If the ears are adjacent to the gun, there's no extra movement time to get to them. Grabbing with one muff cup in each hand has them on in two seconds or less. Hands are now free to operate weapon, communication, illumination, etc.
If the situation is such that you don't have two seconds to spare, skip the muffs and grab the gun and do what you gotta do.
If you need to operate a phone with the muffs on, put the earpiece of the phone next to the receiver of the muff. Looks funny, but works fine.