Originally Posted by TyPo311

Your idea is a good idea in theory, hopefully it works. As of a couple days ago it didn't work for me, though I went with a little different angle see blow. Good luck and please report back.
I'm Marriott Gold and just signed up for the Platinum challenge. Similar to other posters it requires 9 stays withing 90 days (though I'd read reports that you get 3 months plus the remaining month you sign up and this ended up being true). I tried to get them to start me October 2nd (hoping that the challenge would run through 1/31/18 and I could potentially get status until 2/28/20). After calling they told me even if my start date was in October the challenge would end, which would only get me status until 2/28/2019. I ended up accepting the challenge for 9/3/17 through 12/31/17. Platinum status should be good through 2/28/2019.