It probably wasn't as long as the triples sets in the 90s? But in 2009 they had green river open for 1.5 hours which was painful, then they opened for themselves as buzz and dale and did a short set, then opened for themselves again as melvins 83 and played all the way through mangled demos, then did all of Houdini with Trevor Dunn. That was a long ass set. Especially starting with an hour and a half of poorly mixed green river. But the melvins end of the set was so killer! That's maybe not the longest set they've done but counting green rivers set it was certainly the longest show I've ever been to.