Customer retention is the second most important thing after having sales come in. It is costly to gain a customer in the first place, but if you can't keep them as a customer you are always going to have a high overhead in marketing and advertising (Turning and burning customers will not give you a good reputation).
Make a plan on how you are going to keep customers long term. Some things to look at will be discounts, new products, customer appreciation cards or emails with a personal touch, and most of all great customer service when talking to them, solving their problems or just following up with them. This process needs to be on point! Have a strategy with steps on what you are going to offer and when you are going to offer it to them. For example when you want to send them a thank you card, birthday card, email, reminder about a new product, new features you have added to the product they have at no extra cost and so on. Every month you should be sending them something to keep your company in front of them. DO NOT HAVE MORE THAN ONE EMAILS GOING TO THEM A WEEK ON MARKETING OR LESS! Customers will not like that most of their email are coming from you and filling up their inbox. They have to many other things going on. Don't annoy your customers. Also ask for their feedback with a survey to see what you customers think about your company and what you can do to improve their experience.