Event rides with traffic on the roads rather sets the schedule. The group can't be 2 abreast all the time. One can't rotate back if there's a car back. Safety first. 3 minutes seems to be a good compromise and is sometimes not long enough. We're talking recreational riders. I've seen folks sit up there and pull for 15'. IMO that's stupid.

OTOH, I once got with 3 racer boys after the Deli Stop on RAMROD and we rode a rolling paceline full gas for the next 25 miles, passing everyone. Of course the riders we passed grabbed on and pretty soon the line was so long I couldn't see the end. But after 25 miles, we were alone again. We did 'em in one hour flat. I was anaerobic every time I came to the front, with a very serious interest in the exact location of the rider dropping back. It was like getting hit by a fire hose. There's always a up-valley headwind on that last section. I was in my late 50s. What fun. Low traffic on that road and a decent shoulder, BTW. They're ruined it now with a rumble strip between road and shoulder.

Way back when, my droogs and I used to go out with a 2 for a leader. He taught us to do rolling pacelines. It takes a lot of practice. I wouldn't try it with just anyone . . .