If patient wearing invisalign how many days faster they can change the retainer ? I said every 3-5 days patient can change their retainer, is it right ?

Twice as fast would be 7 days. But some doctors are doing 3 days. I would say 5 to 7 days. However it is good to let the patient use some judgment too. Patients generally can tell when they are ready for the next aligner so our saying 5 to 7 days is more of a suggestion. It can also vary with how many hours they are wearing their aligners.