well they had to remix it in a radical way, otherwise nobody would listen cuz everybody heard the orignal 200 times. so its not just a remix, its almost a different track.
the two albums for me that required the most time/listens were Pleiadians - Faimily Of Light and Psysex - Hardcore Blastoff
it really just depends on how far the style of the music is from what you're used to. any truly groundbreaking work will require longer time than some formulaic cheeze.