well, I hope this passgas fellow was able to find a reasonably good 559 replacement tire.
re storage, I do tend to keep my folding tires unfolded for storage, I figure the bead is better off not being folded for year after year after year.
Some of my stored folding tires are folded, some are not. I think the thicker tread ones are more important to store unfolded, as when thick rubber tread is stored highly flexed for years, that is where cracks in the rubber may occur. Thus, my thicker tread ones are unfolded.
When I saw tires on a really good sale price, I often bought them and did not use for several years. Stored in the basement, normal indoor humidity and a narrow temperature range in the 60s and 70s (F). But some of my bikes are in the unheated garage. Winter can be well below zero (F) or for example yesterday, 90 plus (F) with a dewpoint in the low 70s. So, I am sure that the tires on the bikes age faster than the stored tires since they have highly variable temperatures and humidity.
I used to store my errand bike outside, but no longer do that. Those tires had a lot more UV exposure than the bikes stored indoors.