Interesting. Thanks for the responses re opportunity cost vs. cash liquidity. It's something I wrestle with frequently myself. Part of me says, "Work, dammit, money, work!" And the other part says, "Yeah, but next time the market loses 50%, how can you be sure 1/3/5 years is enough time for it to recover so you don't have to sell low?"
We're relatively aggressive in our investment AA, though we do have a hefty percentage of our net worth in home equity, which isn't exactly working hard. So the proportion of our net worth that's in stocks is lower than it seems when looking at our accounts online.
So a more complete answer about emergency funds/cash is: about 8 months straight cash, about 2.5 years in untapped HELOC, and about 2 years in bonds. And that's at our current spending rate, which is honestly pretty high, and which we're actively working at reducing.