I'd say it also depends what fares you fly. If you're flying Ys then you can Y-up almost as easily from gold as from plat. If not, how cheap or expensive are you flying. I've had good luck with upgrades on EWR-AUS the past few years, but those have been mostly H (and I don't think I've gone lower than B), thus having a different result than sbm12, subjectively anyway.