I'd say that for the most part, UND is better than most at retaining players an extra year (or two). Jost leaving after one season was unexpected, but the fact that he was the first player to leave after one season since Belfour says a lot.
The year of the "The Pact" comes to mind when Oshie, Chorney, Duncan, etc all stayed another season after all received offers to leave early. Only Toews left that season, but there was no way he was going to stick around for a Jr season.