Well, every four years we inaugurate a new President in DC, so there's a big change in who's getting screwed by who. That probably qualifies as a peak season. B^O

Seriously though, it probably depends on the lady. To me, it seems that the winter holidays and summer months seem to be slow times. Spring and Fall seem to be normal, but not peak.

The visiting talent could probably tell you how hard to get and/or how astronomically expensive hotel rooms can be at certain times of the year. For instance, when the G8 last got together in DC to discuss world monetary policy and the protestors come out of the woodwork you couldn't get a room in a 3-4 star hotel for less than $360 per night. Average rates were above $400.