“How long should Invisalign be worn?”

This isn't a question that can be answered without seeing what you started with in relation to the arrangement of your teeth and bite relationship. How long did your dentist tell you it was going to take? Some cases move very quickly because they are easy cases (not severely crowded) and the patient was very compliant with aligner wear (wore them 22 hours a day), but more difficult cases (more serious crowding and bite maladies) could take over a year to accomplish even if the patient was very complaint with aligner wear. You have some control over the outcome by making sure you ALWAYS wear your aligners (except when eating), but if you want a faster outcome, ask your dentist about using an accelerator like a Propel vPro device every day - it can reduce the time by almost half when utilized.