I believe the signing window will be open until iOS 17.2 is released. I think this was the case for signing 14.8.1 and 15.7.1 until the releases of 15.2 and 16.2, respectively.
If you look at the release dates for 14.8.1 + 15.7.1, and then 15.2 + 16.2, you will see they had similar release dates. I predict 17.2 will be released December 12th (given history), and the signing window for 16.7.2(or newer) will close shortly after.
If you're still on 16.x after a year or so, chances are you'll have to go to iOS 17+