I have bought points 4 or 5 times this year, so bonus points seems to come around every 60-90 days. I have actually bought (and been 'gifted') around 350,000 points this year and all my stays this year have been points. I am at 35 nights now and will end the year at 41 nights. (some of these were booked with points bought last year).

Technically, you can only buy 150,000 or, during sales, 250,000 points per year. So, your spouse or someone else with an account needs to 'gift' you any additional points.

Make sure that you have the credit card that gives you the 4th night free.

Last, I compare the value of the points not to the cheapest non-refundable rate but to the full rack rate as you can cancel points stays, usually, the day before check in. So, they are very flexible. I do not believe that I have ever gotten less than the half cent value of the points and often get a full cent or more.

Buy $1000 worth before the end of the year and give it a try and see if it works for your travel patterns.