This is exactly why Marriott discontinued "5th night free." It was replaced with "Stay 5, pay for 4."

The cheapest redemption in the consecutive 5 nights is the free night.

For every Five Consecutive Nights you redeem (pay with Marriott Bonvoy® Points), you will receive the lowest Point-value Night free.

• Your stay must be Five Consecutive Nights at the same Hotel.
• All-Inclusive Resorts participate in the Stay for 5, Pay for 4 Offer.
• The Free Night will be the lowest Marriott Bonvoy® Point cost night during your Stay.
• Stay for 5, Pay for 4 Offer cannot be applied to a stay comprised of multiple reservations with consecutive nights.
• If you make a reservation for more than 5 Nights we will consider the entire length of Stay when determining the Free Nights. For example, if you book a 10-Night Redemption Stay, we would deduct the two lowest Nights of the entire 10 Nights, no matter when they occur.
• This offer cannot be applied after Check-In to a Hotel.
• There are no Marriott Bonvoy® Point Refunds or Free Night Credits for any unused portions of the Stay.
• The Marriott Bonvoy® Point cost is based on a Standard Room only and does not cover the upgrade cost for a Premium Room.
• Stay for 5, Pay for 4 Award does not apply to Cash + Points Awards, Upgrade Awards, Nightly Upgrade Awards, and Promotional Awards (e.g. issued through Co-brand Credit Card, Annual Choice Benefit, etc.)
• If the Member makes a modification to the Award Redemption Stay, the Member is responsible for changes to the Points required.

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James