Hello!
First of all, glycine-photo does not lose its activity much longer than 6 months. Some batches of glycine I have stored for more than 3 years. Unless, of course, the glycine was originally pure enough. In this case, the color can be up to a rich coffee color.
Secondly, there is a method to recover and purify oxidized glycine-photo. This method is known from an old USSR patent. If you briefly outline its essence, pure glycine-photo can be isolated from an aqueous solution by adding SO2 or bisulfite (metabisulfite), followed by washing the resulting precipitate with bisulfite solution.
Such glycine-photo is stored for a very long time.
I think that in Albuquerque, with your deep tradition of "home chemistry" (judging from what we saw in "Breaking bad") it would not be difficult to do such operations to purify glycine.