We booked ours at around 520 days out. It has seriously shot by because we created some mini milestones / countdowns along the way to give us something to look forward to. First, we started researching absolutely everything - we bought the dining guides from DisneyFoodBlog to decide which places we wanted to visit - that alone took a good couple of weeks to get through. We then started planning each day on a spreadsheet - starting with what park we would visit each day, followed by which ADR's we wanted at which times. Then the first big milestone hit before we knew it - our ADR's (if you're doing any), which for you, is now only around 673 days away. Then after that your FastPass+ reservations, then after that, food pre-order (if dining at BoG). We've been listening to Disney podcasts most evenings to extend the magic and watched lots of videos on YouTube (we really like watching TheTimTracker's Disney VLogs -
https://www.youtube.com/playlist?list=PLF46C75CDA6C7710B). We have been tweaking the plan as we find out new things.
Honestly, the time will by. It really seemed to speed up even faster once we got under 100 days.