M.B.
What part of the shoe is wearing out?
Is it what he is doing when he is wearing them? (Wearing out the toes, for example, on the swings, or dragging his toes when he walks?)
Is it how he puts them on? (For example, is it the heels that are breaking down because he tries to put them on without untying or loosening the shoelaces?)
Take a look at his shoes and see what it is that is wearing out.... and try to address that problem.