600k principal is 24k annually at 4% , that would probably be the minimum for chums situation.
That's the problem w/ investments like the stock market/401k/etc. You're not guaranteed any type of return, but even if you are, as you pull money out, your returns get smaller. Obviously that's ok if you never have to pull more money out than your returns, but if it's 401k you'll be forced to pull it out. If it's any other type of investment, you're probably going to need to pull money out even when the market is stagnant (or losing).
I'm personally becoming less and less of a fan of the stock market. I don't pretend to be particularly knowledgable about it either. I know people get rich off it, but without putting in significant time by me to learn it better, I doubt I'd ever make a lot.
I'm about to reduce my 401k contributions. I would consider stop contributing altogether, but I'll take the free money my employer matches.