VAG PRO/Ultimate plan activation and credits are assigned to your OBDeleven account and are there until you use it to one-click apps or delete your account. The credits and VAG PRO/Ultimate plan cannot disappear from the account until it has run out or has been used.
In most situations, the user has forgotten which account he used before and has created a new one. That also applies whenever the user has logged in with Facebook, Email or Apple ID before linking it with the email account or vice versa.