While not entirely car-free (I have had periods of being car-free), I have ridden 9-miles, 15-miles, 20-miles, 22-miles to and again after Permanents, Perm-Populaires, and Brevets -- most of the perms and at least some of the brevets have included bicycle commutes before and after.
The energy expenditure to get to the rides has never been an issue; I have never considered that there might be an energy expenditure -- not even when I had to virtually race to get to the start in time. Getting back home after the ride, I mentally go into slow-homebound-commute mode and just keep the pedals turning, albeit often at a slow rate / pace.
One interesting thing I found was that the 300-km brevets became easier, feeling more like a slightly long 200. Of course, if you're riding an extra 18-miles (30-kms) or even an extra 40-miles (66-kms) when you do a 200, then your brain and muscles will think that they are only doing a slightly longer 200.
This year, or at least the next couple months, could be more interesting / difficult as I am completely out of bicycling shape --> extra miles might not feel as nothing.
On the other hand, it hasn't always been beer and skittles (
Irregular Velo Adventures: 300) -- and I was in good shape before that ride.