I moved here about five years ago, learned about the museum about a year ago. I now regret not finding time to visit, I'd assumed it'd always be there.
Similar story for me (I don't live in Seattle but I go there every few months). Except...last year we did a family trip where we needed for reasons to split the family for a day. So I used my free day to visit the museum with my oldest son. Feeling pretty lucky now to have had that somewhat random chance to visit. Also the bagel place next door wasn't bad.