I am hesitant to tell you this because I am competing with all of you in terms of booking hotels, especially during school vacations, but I will anyway. 🙂
MOST OF THE TIME, Marriott Rewards and Ritz Carlton Rewards allow you to book hotel reservations on points even if, at the time of booking, you do not have the required number of points to fulfill the reservation.  You only need to have the points in your account with enough time to order an e-certificate for the reservation.  The e-certificate is a “paperless” Redemption Certificate.  You use the e-Certificates to pay for your award reservation up to 24 hours in advance of a stay.  So technically, you have until 24 hours prior to your reservation to have these miles in your account.
However, just to be safe, I would not push it to the 24 hours prior. Â In fact, there will be a message in your account under your reservation that states
“If you have not ordered e-certificate(s) seven days prior to your reservation, customer support will contact you to discuss payment options.”
I would shoot to have the points in your account around the time of this 7 day window. Â Once you have the points, you can then redeem them for the e-certificate. Â e-Certificates are automatically sent to the hotel. Â You do not need to bring a paper record of the Rewards Redemption order to the hotel.
This feature can add so much flexibility to your travel plans, especially if you book these award reservations early. Â You can make your reservations about a year in advance. Â You can use that year to accumulate the points that you need. Â With a lot of time, you can devise a spending strategy that can help you earn the points that you need.
As for strategies, you can use your Chase Marriott Rewards Premier Credit Card and make it your primary card on your purchases during this accumulation period.  You can do the same thing with the Chase Ritz Carlton Rewards card.
Also, if you have a Chase card that earns Ultimate Rewards, you can do some heavy spending on that card as Marriott and Ritz are both Chase Ultimate Rewards travel partners.  Lastly, you can shop with Marriott’s partners or take advantage of Ritz Partnerships to earn additional points.
I have been using many of these strategies over the last year to accumulate my Marriott points for Paris this winter. Â I am still plugging away!
As for flexibility, if you fall short, or if your plans change, you can cancel your reservation for no charge until 30 days before arrival.  So keep that date in mind.  Hope this helps you to take advantage of free nights.  But hopefully you will not be reserving and holding reservations for places that I want to go to as well.  🙂