http://www.techradar.com/news/pixel-2-owners-will-only-get-original-quality-google-photos-uploads-until-2020

One of the bonuses you get with a Google Pixel 2 or Pixel 2 XL is unlimited original quality cloud storage for photos and videos in Google Photos, but check the small print and you’ll see that this only applies until January 15, 2021.

That still gives you just over three years, but it’s not quite as permanent as you might have expected, especially given that the original Pixel and Pixel XL don’t seem to have any such limitations.