Since the introduction of R-class - I've flown a total of 6 segments at a NW Silver (four segments were super low CO T-fares & 2 NW K fares) and I've gotten upgraded for every single one of them - and they've been recoded as an R-fare. I've also been upgraded before the 36 hour mark as well. The earliest I've been EUA'd is at the 42 hour mark before as a Silver on a weekend MR. My last flight which was ABQ-MSP-DCA, the MSP-DCA segment didn't go through the EUA, but I asked at the gate & they rebooked me in P-class on the ticket. However, when I checked my mileage balance, it was listed as P/P and then 3 days later it was changed to R/T (CO ticketed, NW operated)