Platinum Premier normally kicks in after three years of years at somewhere around 125 nights per year (though this varies and is set by Marriott using a formula known only to them) but in all honesty it confers no additional perks in my opinion.
If an associate notices he or she may mention it, but that's about it. The card is issued for one year at a time, and renews when all the other elite levels do, normally February.
Not sure if the criteria is 3 years at 125+ nights per year. As far as I know, it's something like being the top 2% in terms of number of nights stayed in a given year. So if everybody gets bit by the travel bug, the bar goes up accordingly and vice versa.
I first got platinum premiere in 2009 after having spent 130 or so nights in 2008. And for 2010 and 2011, I requalified with 238 and 300 nights in 2009 and 2010 respectively.
There is no additional perks other than the hotel may be more willing to bump a platinum if a platinum premiere pulls the override and pays the rack rate.
An e-mail from MR on April 28th touted:
Enjoy Enhanced Platinum Premier Services
Simplicity. Now you have a dedicated Platinum Premier team on call at one phone number and one email address. Hotel and redemption reservations. Spa, dining, tee times. Questions about your account or your last stay. Whatever's on your mind, our skilled staff is here to help. Just phone 866-576-5696, or send an email to PlatinumPremierServices@marriott.com.
Savings. Savor a delicious discount on dining. Simply show your membership card and receive 20% off meals and non-alcoholic beverages at restaurants and lounges at all participating JW Marriott®, Renaissance® Hotels and Marriott® Hotels & Resorts in North America.
That's about all the "extra" perks over Platinum.
I can vouch for that one phone call number-they are good at problem solving, though they also answer the Platinum Line from time to time.
A check on that 20% off at mealtime--there are limitations (no weekends at some resorts for one) on its use.
In my 5 years as a PP I have noticed some (not a lot of) recognition by associates. Making it the first time resulted in an additional Platinum arrival gift for me and my wife staying in DC).
Platinum Lifetime (not visible to the associates when you check in) works just as well, though the membership card is seldom required at all, and normally glanced at when checking in.
The difference between the two is based on the member's ability to remind the person checking in of their status, I guess.