Do you stay in touch with your clients after the close of escrow?
Do you have a gift for them after the close of escrow?
Do you invite them to parties?
Do you stop by when you are in their area?
Do you introduce them to other clients and friends in the area?
Do you email them or call them at least a few times a year?
Do you send birthday cards and Christmas cards?
Do you send them notice of a home aranty renewal?
Staying in touch helps build a good referral network and also will help you when they are ready to buy or sell.