How long can "effective substantive review" last?

The longest is hard to say. I have encountered patents that expired just after authorization. In other words, it took nearly 20 years from the initial application to the authorization. Of course, there are also priority and split applications.

Under normal circumstances, the actual trial period of a patent is about 2 years, but there are also special circumstances, such as the resignation of the examiner who was in charge of your patent before, and the case needs to be redistributed, so the review time will be longer.

If you want to speed up the examination, you can reply to the complaint phone number to the Patent Office.