Heaven, I've made the drive a few times in the past few years from Philly, but not since the flood. Flown into Nashville or Atlanta and driven over/up the last few trips down.
Will you update us (me!) on how the drive was? Used to take us just a bit over 10 hours from the west side of Philly, with maybe 2-3 gas and pee stops, but timing the Baltimore to DC traffic was the biggest lesson I learned. And I used to live in DC so I should've known better. The drive really usually isn't too bad going home, but I've driven down on Friday and hit that DC/Baltimore metro stretch too early and it was a disaster fighting with all the Fri morning commuter rush hour traffic. 11 hours sounds about right to me since you'll be coming from a bit farther east than me. Good luck!