Sleep put out Jerusalem in 1998, and then then Dopesmoker, which was released in 2003. Aside from the 2014 single "The Clarity," Sleep hasn't done any new material since 1998/2003, depending on which you wanna go by.
So it's pretty damn exciting that Sleep is currently in the studio doing a new album right this second! The band had previously stated that there would probably be a new album in 2017, but now it's happening, and there's a big ol' bowl of weed to prove it.
— Sleep (@sleep_official) April 6, 2017