How long do Virgin Mobile prepaid phones last?

You don't have to order one you can buy one at Target or Wal-Mart and they are made by Kyocera. They are very well made an I have had Virgin for years with very few problems except some trivial billing stuff. Service anywhere that Sprint is since they share everything by agreement. Excellent phone. Excellent company. There is no expiration. They just continue on a monthly basis. I have them take it right out of my account every month.