Hi Ha, thanks for your question.  If I understand your question correctly, the answer will depend on how many roles and what level of roles the headhunter is working.  For example, if your headhunter (HH) is working mid to senior level roles, and if those mandates are infrequent, then yes, CV's will be screened generally once against those roles, and probably not for some time thereafter if the HH is more of a generalist rather than a specialist.  However, if these roles are frequent, then headhunters will utilize their database wisely to see if there is a match with candidates they've screened in the past.  In my experience, the best senior level candidates I've placed are not the active candidates who have up to date resumes on job boards, but rather candidates that I have had to headhunt.  I find that the great candidates are very busy being good at what they do and that good HH's will find them.