Like to plan ahead.

I'm presently Marriott Platinum. Here is what my normal travel each year:

2 free annual nights from RC CCs
5 free annual nights from MR/SPG CCs
15 annual elite night credit (any CC)

This leaves me with 28 more nights to maintain Platinum. I can think about another 10 nights of travel for the year. So I'm about 18 nights short. I'm not sure if there is anything else I can squeeze out of.

The easy (or hard) way is to spend $75,000 to get to Platinum level just on spending and worry nothing about the night credit.