Hi Ralph! You can keep a citrus tree in a container for a very long time. However, it will need regular root work to prevent the tree from becoming root bound. How long you can keep it in its current container without root work depends on how long it has been in that container. Also, for long term container plants it is best to use a fast draining medium that is slow to break down. Many on the citrus use some sort of variant of Tapla's soil recipes. (He's a user here that has a wealth of knowledge on keeping plants in containers). Hopefully this sheds some light on your questions. If you need clarification, just ask!

Kristopher