I wear diabetic shoes. When I got my last pair, I was told to wear them for 15 minutes the first day and take them off. The second day wear them for 30 minutes and take them off. The third day wear them for 45 minutes and take them off. The fourth day wear them for 1 hour and then take them off. The fifth day wear them as long as I wanted to.
It was the easiest thing to break in the new shoes. And its some good advice and I didn't get any blisters on the backs of my heels.