Great question, recently the National Institute of Health has come out and said that unless an individual has a higher than normal risk of developing heart disease, once a year is sufficient. If you have two or more of these risk factors or already have heart disease you may want to go to 6 months;
High Cholesterol
High BP
Over weight
Smoking
Family history
This is a question you should discuss with your doctor as they know your history and can give you the best answer for you.
Hope this helps,
Jon
Thanks Jon for the response, certainly appreciate it, makes sense indeed.