I Have 15 Sets of Invisalign, How Many Months Will It Take to Be Done with Treatment?

If all goes as planned, the math goes like this: 15 X 2 / 4.  30 weeks is about 7.5 months.

 

Now, if an appointment is missed or rescheduled, it can alter the time, as in 8 to 8.5 months, or if teeth don't move as planned and refinement is needed.

A general rule is 2 weeks per tray.  If you do not need refinement treatment would take approximately 8 months.  You should wear the trays 22 hours per day to get the best results.  If you require refinement it will take a little longer to complete treatment

As your doctor told you: A general rule is 2 weeks for each set of trays. If all goes well and you don't need any additional refinements along the way, your case should be complete in approximately 30 weeks, or 8 months. Of course, a lot depends on your wearing them religiously at least 22 hours/day.

Each tray should be worn for two weeks according to manufacturer recommendations.  Some people push it to 10 or 12 days to speed up the process.  There is some risk to accelerating treatment.  I would recommend going by the guidelines and focus on long-term health and results instead of just trying to be quick.