I have many pairs of ballet flats and wear them to work or for walking during a typical day.
They are very comfortable, but I'm not sure I would wear mine for long distances of walking. I don't think the thin soles would hold up and I want my shoes to last a long time without having to go in for repair (which after it's done, never looks the exact same to me).
When I go for longer walks, I usually wear my Chanel Sport shoes.