The first year we went to Disney, we did 7 days in the parks, and did a lot of criss crossing, and I did a lot of running for fast passes. I had a fairly new pair of Sketchers I had purchased for the trip, and an old crappy pair of $15 sneakers from Wal Mart. I put several miles of walking around my home town on the Sketchers before the trip, and was very comfy in them, until the first day of the vacation. By mid day the first day, my feet were miserable, and I thought the trip was going to suck for me.
Absolutely the ONLY good thing that came out of us trying to take mid day breaks was the opportunity to change from my nice new Sketchers to my old beaten up $15 Wal Mart sneakers. My feet instantly felt like they were home when I put those sneakers on. I wore them for the rest of the trip, and walked miles and miles in them, and my feet never bothered me a bit for the rest of the trip.
Last summer, I bought a pair of Nike sneakers about two months before the trip, and made sure I broke them in very well ahead of time. I took along a pair of the Wal Mart sneakers just in case. The Wal Mart sneakers are still sitting here pretty much brand new. I've worn the Nike's just about completely out, and they still feel great on my feet.
I guess I'm pretty lucky, at 40 years old, being somewhat over weight, and diabetic, I should probably expect to have problems with my feet, yet I am able to walk all over Disney World (and believe me, we walk a lot in Disney), and don't have to spend a ton of money of foot wear. I buy cheap socks, and don't ever spend much more than $50 on a pair of sneakers, and my feet are happy as can be, just not in Sketchers.