The correct number of shoes to own:

I'm not Imelda Marcos, but I think I lost count at 12..

How about snowboard and ski boots?
Ice Skates?
Snowshoes?
Water shoes?

I live where we get weather, so boots means a pair of very warm boots for winter/snow, plus a pair or rubber boots. I happen to own hip-waders too.

Then I have everyday shoes, and an old pair that I wear in the workshop.

Work boots -- with steel toe and all that. Hiking boots since the work boots are a bit too heavy for long walks.

And dress shoes.

At the moment I also happen to have a walking cast, since I broke my foot. But that's not a pair.

Fair enough. So how many and what kind of wheels do you have?
I got by with five pairs of wheels - a collapsible outdoor chair and a rigid frame superlight chair with two sets of front wheels - indoor/dancing only and indoor / light outdoor.

Alternating two shoes daily is proven to increase the usable life of those shoes in relative terms. Many advocate having at least a 3 pair rotation.

Shoes need time to remove moisture. Not only does moisture promote the growth of bacteria, but it directly damages the leather. Good shoes should be rotated, never worn two days in a row, and have cedar trees inserted. This will protect the leather and the shoe.

After 3 years, your well-maintained shoes should get resoled...

There is nothing stopping you from wearing them again if you have to, but to ensure longevity, I would say you could easily get 50% or more additional life by allowing the shoes to dry (cedar shoe trees are also helpful). Of course, the first bit that wears out is going to be the sole in 99% of situations so unless you have already figured out how to go visit your local cobbler when the sole wears out (or rather if you haven't forgotten since that is what everyone did in the past), then rotating shoes will probably not benefit you at all since the sole will wear out and you will throw them away.

Of course this is slashdot where people think that having anything more than a pair of brown and a pair of black shoes is overkill...might as well go the full steve jobs and wear the exact same shirt and pants every day too (ok, fine, your closet can contain both white AND light blue shirts but no stripes or no checks or no greens because what is this a fashion website? what a waste.)