Originally Posted by
prestonh
There is a metro train connection now between the airports so it is not as bad a transfer as it used to be.
To add info to the above great suggestion... it seems to only takes about 1+ hour between airports via the metro subway Silver out of IAD to Yellow or Blue.to DCA. Seems like you could spend time having a drink/meal/site-seeing after departing IAD and stopping at some neighborhood before you finally go to DCA about 90 minutes or less (weather/status/CLEAR/lounge access dependent).
With 6 or 7 hours to transfer...you have many options!