Good keeping property is something I like to have in my chemicals, though I don't know about the shelf life of single stock solution preparation of D-76Ad. Before, I asked you whether D-76H exhibits discoloration when it dies. You said you never kept D-76H so you didn't know. Guess what, I know it exhibits brown tint when it's going off.(posted 8324 days ago)I kept my XTOL stock solution in PET bottles for months with no visible change in image quality. Some (you) may argue that this is not always the case. We don't really know whether this is EKC's fault or not, though many think so. Gainer's Vitamin C formulae have no sulfite, and it's no surprise they don't keep well. You know, FX-1 doesn't keep well unless you make a 10X or perhaps 20X concentration. Ilfosol-S seems to keep well before dilution. I haven't heared a single complaint about Ilfosol-S yet. Guessing from all these combined I think ascorbate formulae don't necessarily have to sacrifice their shelf life when properly prepared and stored.
Right now, my interest is whether ascorbate version of D-76d and buffered FX-1 really benefit from ascorbate or not. If the answer is affirmative, I'll try to prepare long-lasting stock solution then.
PS. I usually use tap water for photographic use. The tap water in my city is really nice soft water that I have no problems with. Activated charcoal is all I need for my coffee and tea.