How many nights stay does it take to reach Platinum Elite?
It takes 75 nights to reach Platinum Elite.
Marriott Rewards | Member Benefits At A Glance
Rundown of all published levels found at the link above. As others have stated, 75 nights are minimum threshold for Platinum at this time.
In addition to spending nights on-site, you can accrue elite night credits via the Marriott Rewards Credit Card from Chase. I believe they award one night's credit for every $3000 spent on the card. The credit card also accrues Marriott Rewards Points along with other benefits.
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