If you haven't had any trips lasting more than 180 days per trip, you're good to fill and file (filling is an action of completing the form and filing is action of submitting the form) 90 days before your 5 year anniversary or being a resident.
I would not recommend filing strictly 90 days before the anniversary. Better to wait a week to ensure you're well within the window.
In short, you're OK filling the form prior to this date, but not filing until you get closer than 90 days to your anniversary.
Good luck!