Businesses look for the first sale and rarely set the stage for repeat business. It's extremely important before you sell your first product to already have your follow-up product at the door and waiting. If your customer has purchased from you once, there is a good chance they will again. You have already established a certain kind of trust with your customer. Do not let them down and never rely on one primary product to carry your business unless it is a daily livelihood necessity like food and water.
Product development is an integral part of any business.
If you want to stay in business keep your present customers coming back for more through product development and highly effective customer service. If It's Not Broken. The fact is, it happens every day. Businesses find a winner and hope they can create a new one. Now that is not to say that you should not test new marketing ideas, but never drop a winner because you are tired of using it or feel the market is tired of seeing it.