How Do You Keep Great Tenants Long-Term?

I have an awesome tenant who pays on time, takes care of the place, and is super easy to work with. I’d like to keep them around for the long run if possible, but I’m not sure what actually helps tenants want to stay.

Has anyone had success keeping good tenants for long periods of time? What worked for you? Should I provide small upgrades, rent incentives, lease flexibility, or is it really just about having solid communication with the tenant?