When you’re playing a three or four-band club bill, every slot has its advantages and its disadvantages.
The headliner is, of course, the headliner, and therefore considered the best or most important band of the evening, though the downside if that’s your role is that you’re probably a little edgy for most of the night before taking the stage. The middle bands can play to the biggest crowd, since some people come late and some leave early, but you have the pressure of a quick turnaround, hastily putting your gear up on stage, and then quickly hauling it off. The openers get to play and then spend the rest of the night enjoying themselves. They may play to fewer people, given the late arrivals, but they have the luxury of leaving their equipment set up in the optimal position on stage after soundcheck and before the set, though the soundcheck almost never happens as scheduled.
Time is a nebulous concept in rock ’n’ roll.