Creative idea,
eethanshire Since I also couldn't get the large tropicana tray in my burn out oven, I went for the smaller one that could, Tropicolino(?). Yet, it was to small, and was wearing out my brush tips quicker going across the grainier ceramic surface. That's when I went to the
Line, to get a bigger size and to be able to clean it easier, yet, now I'm paying for membranes instead of brushes
I do the same thing as you do, in adding porc. to my favorite mixes that stay on the slab, and in my case it can be for a month or two before I start over. Shofu Vintage and Vintage Halo are very stable (all mineral..I think) so I've never had any issues with it going wonkie on me. Vintage MP is a different story, as it seems to be humidity sensitive after so many days on a humid tray, and will turn gray or get blotchie looking (at least for me it did). The old OPC Low Wear porc. (as well as 3G) were also humidity sensitive, and it used to come with a humidor cap with desiccant beads in it (image below is and example) so I guess it depends on your porc. system and if you were to notice any changes.
I found in the past, if I only used a build up liquid to keep my tray hydrated, that over time the liquid would condense, or get more potent in the tray and start causing cracking in my build ups (separation) due to it being over dense, or not drying out normally like it used to. If I was maybe changing my porc out every 3-4 days, may have helped? So I went with distilled water and a bit of Humidistat liquid in the water, to keep the bacteria and mold down.
Now if you mean untouched over 3 days and the porc. dries out due to not keeping the sponges hydrated, would be a concern, in that you would need to remix them well, to get the bubbles out of the porc. as it re-hydrates.