The average (and Invisalign taught way) is 2 weeks for each Invisalign aligner tray. Some offices have rushed it and done one week each, but the cases relapsed very quickly. Three weeks is the most I would do, but even then that is a bit long.
The folks at Align have a lot of experience, so their advice is likely accurate. You may submit an alternative to see if they think it would work. I would consider regular braces instead. Much more predictable and faster.