It has long been a mystery what happens to the free lifetime supercharging that comes with the use of an existing owner's referral link/code to order a Model S, X or Performance Model 3. Tonight, Tesla quietly updated their referral info page to explicitly state that "Owners can give five friends free, unlimited Supercharging with the purchase of a new Model S, Model X or Model 3 Performance. After September 16, 2018, full unlimited Supercharging will go away and owners will be able to give friends a $100 Supercharging credit." Therefore, if you want to lock in the free UNLIMITED lifetime Supercharging, order your S, X or Performance 3 before end of day on 9/16/18, as $100 really isn't much at ALL in comparison to what you get now. (and if you need a link, let me know via private message please). Good luck!