You do not say when in December you'll be going, but it could be busy. To be safe I would book no later than 4:45, just in case Les Chefs is running late.
As a PP mentioned, he makes a specific circuit of the restaurant and doesn't back track. We were there one day when Remy came out and we were probably the 6th or 7th table to be visited. At the same time a party was being seated at what would have been the 3rd or 4th table on Remy's circuit, but Remy didn't come back to them even though he was still nearby.
He only visits each table briefly, but it's a great experience. The entire circuit takes about 50 minutes.
Kim T