@TheObnoxiousDad@realstephen_j@elonmusk Time seems like the big challenge with level 3. Level 1 could conceivably happen in a human's lifespan (maybe ours) and level 2 in several of them. Level three would require millions of years of traveling and expansion due to the size of the galaxy.
@SawyerMerritt I honestly don't understand SpaceX being worth so much, love Elon and SpaceX, but they just need to grow like a hundred times over to justify this and I don't think that growth will happen on a short timeline.