Is the only way to get platinum SPG status is to have 40 stays. What are the benefits of platinum over gold?
You can reach Platinum with 25 stays.
Benefits over gold include 3 points per dollar,
better suites, 1,000 bonus points per check-in (at most locations).
If you make 50 nights, then you receive 10-Suite certificates:
Quote: "After 50 eligible nights, receive 10 Suite Night Awards that you can redeem for upgrades to suites and select premium rooms."
Standard platinum info (25 stays) from SPG site:
As a Platinum member, you’ll enjoy all the benefits of Gold status, plus even more rewards:
Earn three Starpoints® for every U.S. dollar spent on eligible stays — a 50% bonus over Preferred.
Your choice of welcome gift upon arrival — choose from bonus Starpoints, continental breakfast or local amenity.
An upgrade to best available room at check-in — including a Standard Suite.
Complimentary in-room, high-speed Internet access.
Complimentary health-club, Club-level and Executive-level access.
Guaranteed room availability when your room is booked by 3 p.m., 72+ hours prior to arrival.