Or god forbid, you work a little bit to supplement your nest egg during those 43 years.
The reality is that as you get deeper into that 43 year period without pursuing your career, your marketable skills will diminish as well. Many careers don't "scale down" either. A person who was once making $50k may not be able to make $25k with half the hours. The choice in many careers is 100% or 0%. Programming is in many cases a wonderful exception, so that might be biasing folks here.
You may very well end up just getting a part-time retail or fast food job. In any area of the country where this plan is viable, the minimum wage is going to be quite low, possibly as low as $7.25/hour. You're going to find yourself working quite a few hours just for a "little bit" of supplemental income. Indeed, if you needed to cover all your expenses (but nothing more), that'd be a full-time year-round job at the minimum wage (and in fact you might have to work overtime).
If you continually only withdraw 4% of your nest egg (reducing your absolute withdrawal during market drops), then make up the difference if you need to in order to cover current expenses, then you'd be just fine.