Most played and most influential live double in my world was the 1969 Live Dead.
In 1969 it was unique, the opening track was the whole of the first side and continued well into the second side, in fact the first 3 sides of the album are more or less continuous, with just the one edit forced by a change of tape.
Technically very advanced for its time, separate recording desk and 16 track recorded, first time ever.
The version of Dark Star that opens the album is still considered by many (myself included) to be the best ever recorded and possibly the best playing, Garcia's soaring guitar still lifts my spirits, even 50 years on.
“Greetings from the West” by Dan Fogelberg. I bloody dare you to give it a listen, it’s not at all what you’d expect. And, relating back to an earlier thread, the last encore (“There’s a place in the world for a gambler”) is the song that will play at my funeral, and the mourners will be required to sing the choruses.
“Until next time people, thank you, god bless you, good night”! (Ok vicar, you can send him into the flames now)
Steve Hillage 'Live Herald' is one of my favourite albums, although technically it's a 1.5 rather than a double as the 4th side is a studio set (including, I'm sorry to say, a track featuring Jimmy Pursey on guest vocals).