Getting customers can be challenging at first. It takes time to build up trust in a person for them to commit to a product. But over time a business can work out the tricks and rules to entice customers. Getting that same trust, but over the course of a lifetime, in one customer, that is a whole new level.
Here are some theories of what could work.
A product that is constantly changing and evolving is interesting all the time. If it continues to gives value in different ways to a customer it will remain interesting. The challenge is to come up with a product that changes and evolves for years.
Something that is always popular will always sell. If something is popular for a very long time it can even become ingrained into a societies culture. When buying something that is popular becomes a way of life for a person, it takes a great amount of energy for a single person to change that. Examples of this include extremely popular fast food restaurants and soft drinks.