There is already enough material in the book itself to go five quality seasons, they don't need to look up Tolkien's notes and, in all likelihood, embellish on them to make prologues and such. Imagine if they fleshed out Frodo's journey out of the Shire, with the parts with the Elves talking about the old days, and depicting the flashbacks to it of what these legends are about, while staying within the current season.
We should all be rooting for Amazon to succeed but the Lord of the Rings will always be intended to enjoy by yourself, at your own pace, in your own reading voice. The fact that we already have three amazing movies makes this such an impossible task.