I've been intrigued by the actual mechanism of Vitamin C as a developing agent ever since I first read about it.(posted 8650 days ago)
I asked my local pharmacy for some pure Ascorbic acid (vitamin C) powder, and was told that it wasn't kept in stock because of it's poor keeping qualities. I had to get it to special order. The pharmacist reckoned that 3 months was the limit for unopened brown glass bottles of the powder. Presumably the solution suffers the same problem.
I still don't know exactly how it works (when it does work), and to be honest, apart from its low cost and low toxicity, I can't really see any advantage over more conventional developers.