Your son hopefully is intent on making his life meaningful. Perhaps he fears failure in some manner, afraid that whatever he undertakes will ultimately have no impact. It's good that he's working with a therapist. If stress builds up between the two of you, you might also consider consultation with a family therapist who can perhaps help you both explore the reasons behind his difficulty in leaving home. As far as putting deadlines on him, I'd say that depends upon the effort you see him putting out to resolve the situation.
Tough love is usually easier said than done but can have some impact.
Keep in mind that the goal is to help your son leave home successfully. That may require a balance of patience and toughness. He is the author of three books on psychology and spirituality. Although every effort is made to present accurate information, security is imperfect and unintended errors or mischievous material may be present. Please alert the Webmaster to anything that seems wrong.