Every day of vacation. It's the way we wind down for the evening. We usually do a 6:00 or so reservation, finish about 90 minutes later, then head to a park for the evening.
We have been doing this on every vacation for as long as we have been going. My kids are now 5 and 8, but even when they were little, table service each night. It's a way for us to rehash the day, calm down, etc.