If you notice the difference, then it is a fair observation.
As to the CAUSE it could be any number of things.
♦: They actually got home at 5, and by 6 they are two beers in.
♦: They just finished supper and they're well fed and feeling lazy
♦: They have 1/2 their attention on the news on TV
♦: The teenage daughters boyfriends have all arrived and are making rude comments about his bald spot, and they're all tilting
Before black friday, 18:00 to 21:00 Pacific time was a superb time to play, since on the E coast of the US it was 21:00 to 00:00 and the villains were getting more and more tired as time went on.
If you find a good time, exploit it!