When I was younger I, too, used to live in flip-flops, sandals, and generally comfy, unstructured shoes. I used them on many trips to WDW. I 'm on my feet all day at work ( I'm a teacher). Extended use of these shoes over time, added to my advancing years, resulted in a case of Plantar Faschiitis in both my feet. I was in constant pain. I couldn't walk from one end of the mall to the other. Even Grocery shopping was torture. I never thought I would be able go back to WDW. After more than a year of physical therapy, wearing night braces, and finally surgery, I walk without pain. BUT I have to wear shoes with support at all times. My podiatrist's advice to me: NEVER go barefoot for more than a few minutes, don't wear unstructured slippers around the house and wear good shoes or walking sneakers with arch supports. Flip-flops and inexpensive sandals are out. You may find them comfortable now, as did I at one time, but it is possible you may also have problems later on in life.