Things are reasonably peaceful, not having a finger on the nuclear button for a bit isn't going to be a problem.
No. An interruption in continuity is a grave problem.
We never skip a day or two of someone being THE nuclear command authority becase no one has the authority to decide we can skip a day or two.
It does sound like a decision this administration would try yo make, but there's an Air Force general whose job it would be to never leave the prez or vice prez alone until someone is designated as the authority.
Thus would be like taking a nap while driving becsuse the road's straight and the car's going straight. You can't do that.
Or, as you say, maybe the decision was made a while ago. Maybe Esper has two scuffed briefcases in his office at all times, mum's the word.