we drove a couple of times this past year, once last summer and again in March. We live in central Jersey, the shore area. It usually takes us about 18 hours total time, with our 2 children. We are planning on possibly doing it again in a few weeks. I can't find airfare for later this month when we want to go under $300 p.p., so we are considering driving. It can probably be done quicker, but we have always encountered traffic somewhere! We even encountered terrible traffic around Orlando when returning this March. I know some have made it quicker, but we never seem to have that luck. We only stop for a fast food lunch, then sometimes we will go into a fast food place for dinner.
We don't drive thru the night, but plan on leaving around 4-5:00 a.m. on a Saturday. Just plan on your time avoiding DC traffic.