I know how you feel--I've got a decade's worth of shoes around here. I wear a 13EEEE running shoe (and I'm not a runner, I just need the shape), more likely than not a shoe store will have nothing that fits. Thus when I find something good I stock up.

At least for the trails I can so far reliably get shoes that fit, although even there there's none to be had in town, they have to be ordered.

Won't they degrade over time sitting in your closet?

That's a good question and I should look into that but so far they come out like new and I've been doing this for more than a decade now.

I've understood that it's better e.g. for the soles of hiking boots if the boots are used somewhat regularly. Polyurethane degrades due to hydrolysis, and apparently using the shoes regularly (and letting them air and dry properly afterwards) reduces that. The movement and pressure help reduce moisture absorbed into the sole, or something.

It probably depends on the material of the sole, though.

I'm currently cycling through 4 pairs of Hoka Rincons. They're stored in their original boxes and placed in a stack on my garage floor. I grab the top box and replace it to the bottom when I'm done for the day. I actually think this is fairly ridiculous but what can you do...

I've had this happen to boots that were stored for a few years. The soles split in the middle, not at a glue layer. It was like ripping foam apart.

Around 10 years out the glue will fail, seemingly all at once. I have boots 20+ years old which are still great (stitched and nailed), but all the old shoes just fall apart wherever they were glued (the sole usually). You can try to reglue, but it can be hard to get it smooth and walking on a lump ruins it.

Well, so far so good, and yes, I'm still below the 10 year mark.