Apparently whenever the head coach wants to. My daughter started competing in the spring invitational season ( 3 meets) 2013 and we got a beautiful leo that the other girls had only worn in the previous fall season.. For fall 2013 a new leo was needed. Coach decided it needed bling, worn 1 meet, coach didn't like the bling, a new leo was needed. It was worn for 4 meets and it was decided the straps were too narrow. Spring invitationals 2014 a new leo was ordered to replace the one with too thin of straps. 4 leos in 12 months. The last leo was worn for a full year, but I gladly would have bought a new leo to replace it because it was ugly, white that became dingy, looked awful on my pale blonde daughter, and needed a liner that that was so tight that it took 2 people to get my daughter into. Most of the moms at our gym are a little bitter about the leos.