Exactly how do rollover nights work when you reach the next level? My question relates to what you gain or lose by achieving platinum...
After reaching Gold @ 50 nights, any nights earned beyond that rollover to the next year....
If you earn 75 nights, and move to platinum, the nights beyond 50 are used to get the next level....
If I earn 65 nights, I roll 15 towards gold the next year.... Gold is actually very good....
If I increase those 65 to 75 nights, nothing rolls over....
Is Platinum actually worth it??
Platinum, and all, benefits are spelled out on the Marriott website.
Platinum benefits are found here: Learn about Marriott Platinum Elite Benefits
A comparison of all elite levels is found here: Marriott Rewards | Member Benefits At A Glance
Whether or not it is 'worth' it depends on your travel patterns, brands, and so on, for the incremental differences between gold and platinum.
As for your question about rollover: whatever 'new' nights earned in the current year exceeding the requirement minimum for an elite tier level, but less than the next higher elite level, will roll over to the next year. There are multiple threads on that in this forum explaining in more detail and using mathematic examples. All 'new' nights above the platinum level will roll over as there is no official published elite threshold above platinum.
In your example above, yes, that is true, nothing rolls over if you hit 75 precisely. Each member needs to decide what works best for them. Perhaps you would be better off having those same nights in the new year, so you would be on your way to next qualification.
The differences between gold and platinum are not huge, but they are certainly measurable, and many would say that gold level is the real sweet spot of the MR program. Your mileage, of course, may vary. If you are working for a lifetime status level, the point reward difference between G & P is substantial.
The concept of rollover nights is interesting. The goal of having them is to help retain status. So by getting to 65 nights, you'd rollover 15 nights (assuming you had zero rollover nights from last year since they cannot rollover again). This will help you reach 50 nights more quickly and retain your Gold status. If, however, you get to 75 nights, you become Platinum and, as you correctly noted, would rollover nothing. If you fail to hit 75 nights again next year, you would not qualify to retain your Platinum status, but even if you fail to hit 50 nights, you would only drop one level back to Gold. So by reaching Platinum, you guarantee at least Gold status for two years. Personally, if I thought I could reach Platinum in a given year, I wouldn't worry about rollover nights at all. The additional points earnings are alone worth it. Most of the other differences between Gold and Platinum are modest.
In the long run rollover nights are meaningless with two exceptions. They give you a head start on reaching your nights threshold and they help bump up your lifetime nights. You might read How to Calculate Rollover Nights for more info.
Short answer. Unless you need to increase your lifetime nights (to gain lifetime status) don't worry about rollover nights. Go for Platinum.