Yes, you will have plenty of guests. You will be astonished. I live in Boston, and I would imagine that you might get people at your place for similar reasons that I do. Aside from tourism, you will find people come to DC year round for a variety of reasons, particularly:
-dropping off/picking up/visiting kids at college
-other professional reasons (interviews, meetings)
The professional visitors, I have found, tend to stay for 3-4 nights, which to me is a perfect length of stay. I'm not doing a changeover daily, but the stay is quick enough so that I'm never feeling like someone will never leave.
Hillary! Thanks so much for the response. I appreciate the info you provided about your experience. I agree 3 to 4 nights is the best length of stay. Do you set your calender so that people can only book a minimum of 3 nights and if so, do you find that there is enough demand with that setting?
I find that business is good all year round! February is my slowest month, but I still got bookings even then.
People tend to make Air bookings within 2 weeks of their stay, so you'll probably find fall and winter bookings coming in quickly when it's closer to those dates.