Just did a century on Saturday with a good cycling friend, and we did 5 mi. pulls the whole way. It was a good distance, we weren't riding for a lot of speed, and there was a fair amount of elevation along the way (6000 ft total gain) so in spots, wind resistance because less of a factor.

On the roads where I ride, I'd feel uncomfortable changing up every 30 seconds, because of car traffic. Everytime you switch up, you have to ride side by side for at least a few seconds.