500k at 7% per year (common number used for the growth of the market as a whole, and thus the average growth of index funds) means $35k/year, not an unreasonable salary to live on.
You don't have the option of just withdrawing $0 on your "down" years.
p.s. if you can find a risk free 7% return on 500k, open a retirement planning business, become very wealthy.
Well, you can live on it assuming that unexpected issues do not arise, plunge you into medical debt and render you unable to receive the best care you might otherwise be able to afford. That can cut short your "living on 35k a year" plan... A sad story many of those 35k/year Americans can likely talk about.
Given the option of retiring now and living off of 35k/year for the rest of my life, or continuing to work for several more years, I am going to continue working.
If I had to have a rough guess, my minimum retirement target is $300,000-600,000 of personal property, plus a moneypile or otherwise low/no-work income (if I were working an insignificant number of hours at something I could stop anytime but enjoyed doing, I would still consider myself retired in the conventional sense) yielding between $20,000 and $40,000 / year.
So, using the 7% figure from the GP, that puts my target retirement assets at around $600,000-1,200,000.