Whether you are an investor or Owner Occupier eventually your loan and interest rate will get stale. Your lender will stop giving you interest rate decreases. This means that after a few years you will be paying more on your home loan than you would if you moved to a new lender.
I recommend that every person with a home loan have their loan assessed by a broker regularly to ensure you are getting market leading interest rates. By moving to another lender with a better interest rate you will ensure your loan is working at peak performance and that you keep more cash in your back pocket and not the banks.