When you forward your resume to recruiters you know or send it via e-mail to a targeted group of recruiters you have identified, you may get one or more calls immediately, or you may experience total silence–at first. A former internal recruiter in a professional forum that I participate in indicates that she held on to resumes of quality candidates for one or two years or even longer, waiting for a job requisition to come up that was a match. I have personally had numerous clients and friends who received calls months or years later from a recruiter, many times resulting in an exciting career move. So liberally plant those seeds; you never know when one will sprout.
On a related note, while statistics generally quoted say that recruiters fill just one to three percent of jobs, when you restrict the universe to high-level management and executive jobs, that picture changes. Think about it: If you were to suddenly vacate your current position, what would be one of the first steps your company would likely take to start the search for a replacement? More than likely, they would retain a recruiting firm.