Just a crazy thought, but if she worked just a couple more years, couldn't you BOTH retire or drastically cut back on work?
You seem like a great guy and supportive spouse, but I wonder if some resentment would build over time if your wife really did spend her days "riding her bike", etc., and you're doing the school grind into your 40s and 50s.
And honestly, you might fire back with "Of course not, Nick, that's ridiculous, " but I think it would be hard to anticipate how feelings might change over the next decade or two.
Speaking personally, even if I was okay with it for a year or two, I think I'd resent a situation where my wife left a hugely high-paying job, at a relatively early age, thereby locking me into working full-time for another 20 years.
Have you pondered any of this?