It sounds like you found a good dosage. If you are feeling better and don't have any negative side effects, there's no real reason to change anything.

If you decide to try to "get off", make sure you do it with your doctor's permission, since it shouldn't be stopped suddenly. Long-term use has its benefits, but it can also increase risk for certain issues, such as elevated cholesterol and liver problems. However, those are some things your doctor is probably aware of, and if he thinks it is best to stop taking it at some moment, he will tell you.