Last month I mixed up some Ansco 130 with glycin that was stored at room temp for 4 years. I'd been warned that glycin does not last long, and the glycin powder had turned a pale brown color. Despite that, I mixed some up and the solution had the color of strong tea. Dark brown. I figured, what the hell, and tried it anyway. It worked pretty nicely. I didn't have "fresh" glycin to compare it with, but I can't complain about it.
I know it wasn't the Metol, but it still worked nicely.