Since EMDR is used for a wide variety of clinical complaints, with a broad spectrum of client complexity, there is no overall "typical" course of treatment time. However, the three 90-minute reprocessing sessions (subsequent to history taking and preparation and followed by a session for reevaluation) are typical for an uncomplicated case of single-trauma PTSD. That is, if the sole complaint is PTSD caused by a discrete trauma, generally no more than three processing sessions are necessary. Other complaints, such as phobias which may be caused by a discrete "trauma" may also take three sessions.
Certainly, it would be an error to state that three sessions would be sufficient for more complex cases. However, one-to-three sessions would be a reasonable rule of thumb when assessing the amount of time needed per target.