[This reply ended up being longer than I expected.
420K sounds like a solid number. And in the meantime you have a view of the finish line. The recent market movement is a good test for what makes you comfortable. The market can be way more extreme than the past few weeks, so good to test how you feel during this storm.
The standard early retirement advice would say do a couple years more. For me personally, it came down to a gut feeling that I had just enough
to make it. My plan is to live my life in a very flexible manner, and I have just enough experience doing that to be confident of pulling it off. I think I can have enough invested in alternatives to the stock market (cash, metal, etc.) that I can avoid being thrown onto the street for several years or more before I have to start liquidating stock or applying for traditional jobs. I realize that this approach is not going to feel good to most people.
Also, as I said in the journal, I can't imagine never earning another dollar. I haven't come up with any brilliant ideas yet, but I feel like over the next several years I can come up with some ways to get $5K or 10K a year - even if it's just a low wage seasonal job. That's the beauty of the type of life we are both thinking of - we don't have to come up with $100K per year . . . and we don't even have to come up with $5K extra per year for many years to come.
American healthcare . . . what a mess. I’m thinking of this more as a problem to be hacked than something to justify several more years of work. This year, I’m doing the Obamacare plan ($1 per month!). Even under the proposal that failed last year in the Senate, I would have turned out OK. Not as cheap but survivable.
I think we’re approaching maximum screwedness with our healthcare system - it impacts so many people that at some point a free market alternative and/or more low income subsidies will appear. In the meantime, I have enough assets to absorb a hit . . . I could swing $500/m premiums and $10K deductible for a little while and have time to problem solve my next step.
So in conclusion
. . . even if you go a few more years, you will be achieving extreme early retirement. No need to rush it. But . . . you do have just about every possible advantage in this equation. Young, healthy, proven track record of low expense living, hard worker (I assume), extreme flexibility in terms of location/housing/kids. Your SO may not be FI but she’s not exactly broke. You have enough assets to absorb any number of short-term "disasters" - healthcare or otherwise, and you don't have to even think about extra income for many years. You are close to taking a test drive.