Not that long compared to others here, but long enough to have seen things that work and seen things that don't work, and with sufficiently varied approaches. I think there's reasons why this will work, but I also wonder if they would have screened the startups slightly differently if they knew they were going to do the whole batch remotely. Working in an all remote environment require different communication skills than working in an office.
I also wonder how easy it'll be for founders to put in 16+ hour days while working from home. It's easy to 'stay late at the office', but I think it is harder to contain myself in my office while doing that. Maybe that's just a me thing, but I think it can be a real issue... I wonder if founders will simply hole up in the same living space somehow during quarantine; I could see that working, that's basically I've seen friends who've been in YC do anyway. It just might be harder to do in this environment.