Join Date: Mar 2004
Location: NYC, ROC, HNL, PEN, BKK, KUL, SIN (check out http://my.flightmemory.com/kkua)
Programs: DL Diamond charter member; 2 million miler (45% from NWA, 2MM achieved 5/2018)
Posts: 682
BigLar, I remembered many moons ago, NW required Sat night stays for NYC-SEA. When B6 (JetBlue) entered the market, they've relaxed the rule to EITHER a Sat night OR 3 days for earliest return. So, yes, the Sat night rule still applies (true on JP itineraries).
I'm curious, what are the fare basis on your tickets? Read under the "combinability" section of the fare rules.