I don’t view “optimal length of shutdown” arguments compelling, rather it is about how much pain the political process can stand. I expect partial reopenings by mid-May, sometimes driven by governors in the healthier states, even if that is sub-optimal for the nation as a whole. Besides you can’t have all the banks insolvent because of missed mortgage payments. But R0 won’t stay below 1 for long, even if it gets there at all. We will then have to shut down again within two months, but will then reopen again a bit after that. At each step along the way, we will self-deceive rather than confront the level of pain involved with our choices. We may lose a coherent national policy on the shutdown issue altogether, not that we have one now. The pandemic yo-yo will hold. At some point antivirals or antibodies will kick in: “There are perhaps 4-6 drugs that could be available by Fall and have robust enough treatment effect to impact risk of another epidemic or large outbreaks after current wave passes. We should be placing policy bets on these likeliest opportunities.” We will then continue the rinse and repeat of the yo-yo, but with the new drugs and treatments on-line with a death rate at maybe half current levels and typical hospital stays at three days rather than ten. It will seem more manageable, but how eager will consumers be to resume their old habits? Eventually a vaccine will be found, but getting it to everyone will be slower than expected. The lingering uncertainty and “value of waiting,” due to the risk of second and third waves, will badly damage economies along the way.
Emphasis mine. The one thing I would add is that while the disease is still spreading rapidly the death rate seems to be down. Not sure what that is about – the most vulnerable are already dead? the virus is evolving to be less lethal? – and anyway we can't be sure yet that this is real.