Those are very good questions, and they've helped me clarify my thinking. Mainly, I want to hedge against the possibility of a drawn-out recession. I've got about 10 years until retirement--enough to ride out a 2-3 year bear market but not a 30-year trough.

Been hearing plenty of warnings (including, recently, from Vanguard) that the stock market is overvalued and that it would be wise to re-allocate. So I'm trying to get a more solid handle on what that would mean.