Obviously dependent on the number of comments, let’s call that n. Maybe as often as n^-0.6 in unemotional topics, and closer to n^-1.5 for politics and current events. Comment score is a better predictor of comment age than comment quality.

At 9 comments in 2 hours, it’s already false in this thread.

It’s usually not classified this way, but I consider 99 Bottles of Beer on the Wall a New Year’s song. It combines two of the main NYE traditions – alcohol and counting backwards.