We just bought our first contract in January. I bought the field guide a few months before buying points and read it cover to cover. It was a bit of a re-hash of "free" info I had picked up lurking here or watching YouTube videos. But, I thought it was very very helpful. It's all the information you need all in one place. I think it should required reading for people thinking about buying.
Also, I love the room layouts and resort maps. It's so useful to see where the tiers of room views are located at the resort, and how the room is laid out. Helps to determine if the upgrade is worth the extra points.
So I have the 2025 version, I'll skip 2026, then buy 2027 when it comes out. I don't think it's necessary to get every year... not that I much should change. But good to stay current and support the authors.