Have the first evaporator head for well over 2 weeks in use and it is still steaming as the first day. No kokeln and are accurately reflect the taste, you can smell in the bottle. Have been using this evaporator now 3 bottle (a 10 ml) consumed and notice absolutely no difference to the Joyetech gizmos. If the other Heads of Ricardo also hold for so long, there is a strong buy recommendation, since they are priced so cheap.