I have been missing upgrades all the time this year. I am at about 70% as a platinum. Granted a large number of my flights have been to the west coast, but last week on NW354 SFO-MSP the GA told me there were 28 Plats... on the wating list. Yeah, I missed that one despite checking in 23:55 before the flight on a B fare.

I've even missed upgrades on a full Y fare.