Yep 650 miles is an easy 11-12 hours!!
We're in North Alabama (677 miles from my driveway to the WDW arch on World Drive) and have done the drive many times in one stretch.
I've done it by myself in as little as 10.5 hours.
The longest it took us was with two vehicles, 10 people, (4 adults, 6 kids ranging from 10-15) 12 1/2 hours.
However, we have started splitting up the drive, not because of the length of the drive, but for other reasons stated below:
We drive as far as Ocala going down there and stay at a Super 8. We usually leave on Friday afternoon at 1:30 central and arrive in Ocala about 10:30 eastern (that is the earliest we can cut the boys loose from school) We get up bright and early the next morning (5am) and get to our Disney resort by 7am and get checked in and off to the parks. This usually ensures we get our room requests as we are one of the first to check in for the day.
We check out of WDW the day before we plan to drive home and stay at the parks as late as we wish, (we usually close down Epcot, then go over to Pleasure Island for about an hour) then make the short drive back up to Ocala and stay at the same Super 8. We then sleep as late as we wish (usually 10am) then head on home. We then get home at a reasonable 7 or 8 pm.
The two times we have stayed at WDW the first and last night were not as enjoyable because:
1) We didn't get our room choices
2) On our last day we stalled leaving WDW (we had a big character breakfast and then did some shopping at the Contemporary) and didn't get out of the Orlando area until at least noon, which got us home well after midnite. It is much easier to get up and hit the road at a Super 8 motel in Ocala than it is to leave WDW and everything it offers.
One thing that we have done that makes it easier, is that we make sure we pack one bag exclusively for the Super 8, so that we are not dragging out all of our luggage. When we get to the Super 8, we pull out that one bag for all of us, and that's it. When we repack to head back home from our WDW resort, we make sure that one bag is packed and ready for Super 8 again.
I hope this helps.
Carol