In general you can expect to work with the following timetable, provided clients can meet candidates in a timely fashion. Most searches can be completed within three months; many are even faster.
Stage One:
Hammer out job description with client and position requirements
Present a short-list of clients within two to three weeks
Discuss strengths of clients presented
If needed, refine search parameters and hone short-list candidates
Stage Two:
Arrange intial interviews over a two-week period
Discuss strengths and weaknesses of clients presented
Set up Round-Two interviews for candidates
Stage Three:
Bring back finalists for last interviews over two-week period
Negotiate compensation package and start date
Present offer letter