Pavement and their fan base always has had a slight jam band feel even if set lists are static
It’s famously been said how the Dead played thousands of shows for the same 10,000 fans.
That’s an interesting way of thinking about why you might book certain bands multiple nights; the same hardcore fans see multiple shows as opposed to one big show say at the Anthem.
There is a free date the night after DC show so it’s possible they could add a show in DC…. But I think it’s unlikely as in all their years playing DC they never played bigger than 930