Welcome new people! Glad you are looking at pulling the triggers in 2019 too!
For the big crash question, that is an interesting question as DH and I are going to be right around 4% (maybe more, maybe less) depending on the market when we leave. Since we haven't been high earners most of our careers, we have taken high risk with our portfolios to cut down on time. So if stocks go down, we go very down with them.
So, what is the plan if bad times hit early in retirement since we don't plan on keeping out jobs:
1. We have two years of mortgage payments in cash. Having a cheap house really helps with this.
2. We will also have an additional cash buffer to fill in gaps.
3. Knowing the mortgage is covered, we can cut spending by over a third and still be happy, if less traveled.
4. We plan on pulling money out the year before for tax reasons (2019 money will mostly come from 2018 investments), so we know at what value we will be selling. If things are bad, we can put off pulling out more money and use the cash above.
5. Even though we are mostly in stocks, we have some diversity there. We can draw down from industries that are still in the green, or that are most likely to bounce back fast.
6. If things are really really bad, and we can pull out no money, and all our cash is dwindling, we will have to find a way, between the 2 of us, to bring in ~$24,000 per year to keep us afloat. I have skills, even if not high paying, are highly desirable.