My cost of living is about the same as the typical family with kids attending good public schools along the SF Bay Area peninsula, but the approach should be repeatable in most places. My expenses over the years has stabilized at less than 50% of take-home salary (not including bonuses, equity grants, etc.) for my main job, in line with a previous post of 30% of income. So the absolute worst case scenario for a 4% return is 25 years.

In my particular case, I had saved all my bonuses (both cash and equity) and most of the income from the aforementioned portfolio. I was also fortunate to have held a consistent side job for most of my career.