The SL before the Dakota's joined (2006-07 season):
Valpo (left the next year)
Centenary (left in 2011 for DIII)
SUU (left in 2012)
UMKC (left in 2013)
Oakland (left in 2013)
WIU
Oral Roberts (left in 2012) (rejoined in 2014)
IUPUI
So unsteady. If the Dakota 3 left, that conference would become the Great West 2.0 which would scare me if UND were to join the SL. Who would say the SU's, Omaha, Denver, or anyone else would stay. We already saw ORU leave once, who says they would stay permanently.