With the theoretically-9-weeks-but-who-knows answer, everyone would actually be better off being told, "I have no clue how long it will take," because at least then there would be no false expectations.
Except that generally "I have no clue how long it will take" gets the response of "I need to tell so and so when it will be done" so then you end up getting your 9 weeks answer anyway.
Adapt. Enjoy. Survive.