Huh. So you are saying if I have 2 pairs of identical shoes, A and B, if I wear A for T months, then B for T months, by alternating every day I should get >2T months out?
This is because much of the wear on your shoes does not come from steps and hitting the ground. It comes from sweat and moisture inside the shoe, and the inside of your shoe takes a REALLY long time to dry out fully.
If you wanted to extend of life of a shoe without rotating pairs you can also buy a shoe drying rack. This is what a lot of people in construction do with extensive work boots.
For the price of 2 Allen Edmonds bought retail, I could have 7 pairs of their timeless shoes, rotate them regularly, and never buy shoes again.
In reality, I have 4. 2 brown and 2 black, and that’s more than enough. My Dad has the same, and is still wearing his from the 80s on a daily basis.