It depends on the situation. Many of the shops have Arrive-and-Drive customers. They set up a brand new kart for their customer, and then after the event, look to sell the race ready package. For instance, the European drivers come over for events in America, such as the SuperNationals or the SpringNationals just this month. I’m sure the kart Abbasse, Fore, or Lennox raced on are available for purchase.
In some since, these type of packages are great, as they are already ‘broke-in’ and ready to hit the track without any assembly.
Most karting chassis last a long time, especially for club racers.