Some customers will order from you once and that is it.  Some will be repeat customers and never be a host.  
 
Did you try offering the customer who never wants to date a party....a catalog party?  
 
Customer Service is very key in direct sales.  I am always there for my customers....making follow calls after they receive the product to make sure that they are satisfied with their purchases and if they occasion arises in the conversation I always say something like...I am so glad you are enjoying your purchase...I would love to schedule a home party for you, so that you can receive free and discounted products to compliement your purchase."  But never be pushy......or ask right away when you get on the phone with them......I believe that you have to develop a rapport with them.  If you kind of relax them before you ask them you might have a better chance.  I just learned this through a tele-seminar.......Did you ever hear of Deb Bixer...check out here website www.createacashflowshow.com for some great ideas and free resources.....she does sell some of her training materials......but there is alot of free stuff as well!  I know I didn't answer all of your questions......but I hope this helps out a bit.  Goood luck.