What is the lifespan of your basil plants? Do you grow from seed or buy plants? What symptoms do they exhibit as they are dying? Another thing to keep in mind is that basil are very cold sensitive plants and you will not want to put them outside too soon.
Basils need to be put in a location with good sun. Tell me about your watering practices. The pots you use need to have good drainage. Basils need consistent moisture so you have to be careful not to under/over water. For specific guidelines on how to water basils in containers, please visit the following link:
For more information on growing basil, please visit the following link: