You rely on your hot water unit every day. To help prolong the life of your unit, have it serviced regularly. Regular maintenance will definitely reduce servicing requirements over the life of the product and find small problems before they become expensive problems.
Most manufacturers recommend having the unit serviced once a year by a licensed tradesperson to ensure optimum performance. This is a good basic rule to ensure your appliance remains in good working order.
Your local Reece store can help you to find a local serviceperson for your unit.