Mark Wollschlager
I would try to time your arrival to the dc area ( that would be from Triangle North ) to after 9am.
My wife drives from Alexandria to Frederick for business a couple of times a month.
She finds that the Beltway from 95 to Tysons Corner to be the slowest part due to construction activity. Once you get past there the trip up 270 is pretty quick.
On the way back the HOV lanes south are a pretty good deal and open to all until 3pm. I would try to time your return to hit the Springfield interchange ( the entrance to HOV ) before 3pm.

It's not a drive I like to make, but believe it or not weekdays are better than weekends. As long as you steer clear of the peak rush periods.

Mark.