Earlier quoted context omitted.
Obamacare subsidies are based on income. You are likely getting subsidies at this level of income. Will it exist for the next 40 years, who knows?
A couple years of serious illness for you or anyone you're responsible for (spouse, children) will still ruin your retirement plans, if you try to retire early on $40,000/yr in income. A "Silver" exchange plan, even if the premium were $0/m, would still expose you to so much financial risk ("max out-of-pocket") that you'd be rolling some not-very-friendly dice, trying to retire early.
My out of pocket maximum is something like $7000/year. That would be painful on $40k/year, but we're talking about someone with a $1M nest egg, so unless you hit the maximum every single year, its not impossible to cover. Spending $47k/year for a couple years instead of $40k isnt going to financially ruin someone with $1M.