I don't ride in groups much anymore, but back when I did, it was with a group that started with 8 miles of a double paceline - but not the rotating kind. This one, the two front riders pull out to the left and drift to the back. There wasn't a set length of time, but it seemed like a couple minutes, maximum. After about 10 miles the group split into racers and non-racers, and we non-racers generally did a single line, with people rotating off the front at about the same interval, except for that time one guy really was feeling his oats, put his head down, and pulled all of us into a headwind for almost 8 miles*. That was awesome!
*Larry - North on Foothill, all the way from Loyola to Alpine.
__________________
"Don't take life so serious-it ain't nohow permanent."
"Everybody's gotta be somewhere." - Eccles