IMO, the faster the pace, the shorter the pull. In a good structured paceline at 22MPH, maybe 1 minute makes sense. At 25MPH+, a constant rotation makes sense. Endurance riding at 20MPH, all bets are off.

IMO, the key is everyone in a given paceline needs to pull at least some of the time. I can understand "skipping your shift" once in a while if you're dead, but it's irritating to me if there are riders who never, ever take a pull and just hang out in the back for the entire ride. IMO, expectations need to be set up front over the pace and "responsibilities".