If your authorization has an expiration date, you need to see either that doctor to renew or see another doctor to get another recommendation. The law says that you must be a patient of the recommending healthcare professional.

If your doctor is not going to go to court and affirm that you are their patient that leaves you in a bad spot. If your card is expired, that might be the case. Also, if you want to establish that you are a patient of a doctor (or other healthcare professional that can recommend legally under the law) you probably want to be seeing that doctor at least once a year. Even if your authorization doesn't have an expiration date, if you haven't seen that doctor in a decade, are you really their patient? These are things I wouldn't want unclear going into court, personally.