Generally I try to assess if the customer is trully interested in the product you are selling to them. If they are dragging out the process for reason such as getting approval or waiting on a current contract to end I will continue to grow the relationship and follow with them on a weekly to bi-weekly bases. If the customer does not have good communication and is not following up often I generally will close the lead and follow up with them in 2-4 months to see if anything has changed.