Having been in the restaurant business, I know there are usually 2 dinner periods in a restaurant, depending on the area/restaurant. Usually you can notice dinner crowds around 6pm-ish and another crowd starting around 8pm-ish. I tend to eat earlier rather than later, so I'm aware that the restaurant would like the table free for a second set of customers, so I usually don't linger. If my friends and I want to talk some more afterwards, we try to take it somewhere else, maybe a dessert place or Starbucks or something.