Most patients with primary coccidioidomycosis are asymptomatic, but nonspecific respiratory symptoms resembling those of influenza, acute bronchitis, or, less often, acute pneumonia or pleural effusion sometimes occur.
By using retainers to hold the teeth in their new position for a length of time, the surrounding periodontal fibres are allowed to adapt to changes in the bone which can help minimize any changes to the final tooth position after the completion of orthodontic treatment.
As you know, permanent retainers are not permanent. Yours lasted an atypical amount of time. At some point in time, natural forces should be allowed to take over. Therefore, I would say the following to answer your questions: 1. There is no special time limit that a permanent retainer should be used.