Taking out more than $40k/year erodes your principal though, I thought that was pertymcpert's point?

Like, if you've got $800k and can reliably earn 5%, as long as you're withdrawing only $40k you're good. But if you withdraw $41k one year, your principal is now only $799k. Next year if you need $42k, the return from your $799k is only $39,950, so your principal goes down to $796,950, etc.

From a quick spreadsheet, if inflation is 2% annually and you can get 5% on your principal, you deplete your $800k in ~32 years.

Doesn't seem too hard to fix with some supplemental income here and there?