We don't change them, we buy them for a second year, the previous ones we bought, we wore them constantly and we still have them but they are small, the color has faded slightly from the lines at the edges, due to frequent washing and intense rubbing with a sponge during washing as we wore them everywhere even at the beach (sand, sea, stones)/pool. The material is seamless and does not cut, because it is seamless and has no seams it cannot "hurt" the foot no matter how long you wear them. They do not sweat or smell, they are easy to wash, they dry quickly. The child has enjoyed them to the fullest.
I come back after 3 years to say that we don't change them! The only thing that changes is the colors and the sizes.