@:-) An additional part of the answer to this question is when to do it. Excellent times of the year for hotel hopping are around Christmas to New Years, Thanksgiving, and the days around the Fourth of July if it falls on a good day of the week. These are times when "everybody" (the transient DC population) goes home, and visitors drop to nil. This applies to properties all the way into the District @ less than $100. In DC, they can be $75. The suburban properties, full service included, may be ~ $50. Dulles and Fair Lakes can be the lowest.
It pays to book when you see a price you like (not advance purchase) but keep watching close-in, because they often will go down further.
This used to be a wonderful FFN earning strategy. One of the best things about it is that there's always something to do in and around DC if you can deal with the humidity at some times of the year.