Marc,
Staffing firm usually gets paid by the company per person found and in the amount equal to a 10% or so of the annual salary of that person, so if they think you may be of interest to the company, they would do all they can to employ you (of course, they may have more people to match the position).
As per my experience, staffing firms (or rather recruiters that worked with me) always called back very soon, did all the follow up calls, sometimes several times a day, sometimes asked me to rework my resume, set up interviews, even negotiated a better compensation package, and so on if they considered me a good match for the position. (On the other hand, I once was interested in a position, but a recruiter had a few "more suitable" people for it, and something "more suitable" for me and no other candidates for it. I didn't have enough experience required for the 1st position and plenty of it for the 2nd. So no matter what I said, he didn't send my resume to the position of my higher interest, but was able to employ me very fast and with a good compensation to the one he considered a better match.)
That said, there is nothing wrong with calling them back if you don't hear from them soon enough and ask, how it is going or is there any news for you. If they have several people to match the position, often it is better to remind about yourself and show your interest in the position to increase your chances.
I would wait for 2-3 days, maximum a week before giving your recruiter a call, while actively seeking elsewhere also.
Stella
