My dad was also blessed with extremely (absolutely no arch) flat feet. Blessed, I say, because they kept him from being drafted in Vietnam
Not so blessed because he always had problems standing (especially on concrete) for more than 10 minutes at a time. The older he got, the worse the pain became. The constant impact on his legs was destroying his shin bones.
My senior year of college he had surgery on both feet to essentially rebuilt them (I don't know the clinical term). Basically they sliced into the back of his ankle....I know he has a bunch of screws and such in there. It was an extremely painful surgery, and he was in a wheelchair (having had both feet done at once) for about 2 months-should have been longer, but he's stubborn. Now, however, he's 50 times happier.