actually you are on your 3rd extension of your permission to stay. The visa was an entry permission and was replaced when shown to immi in the airport with a permission to stay - the length of that permission depending on visa. Very important : remember the TM8 (re-entry permission) before you leave - otherwise you'll have to start all over!
you don't renew your retirement visa - you renew your permission to stay. That's why it is called extension of stay. Always ask your local immi for their folder where they describe the requirements since they can differ (slightly) from immi to immi.
always ask your local immi for the folder they have for their requirements because they are not all the same from immi to immi. And your non-o was an entry permission and was basically used when you entered and replaced with a permission to stay - the length of which is based on the visa type.