If you feel uncomfortable, that perhaps you are calling too often– ask. Your prospect will tell you. Say, “I don’t want to drive you crazy. When should I check back?” Most prospects will say, “You’re not driving me crazy. I appreciate the follow-up.” Then they will tell you when to call and of course, call back whenever they say to do so, simply do it a little earlier. You can also ask, “How should I follow up with you?” Prospects will tell you.