Wood can last for centuries. What Can Be Done to Promote Long Service Life from Wood?
The linked document - "Build Green: Wood Can Last for Centuries" provides many helpful tips for homeowners. While this an American document the principles are just as relevant to Australian circumstances
Authors Carol Clausen and Samuel Glass sum up their research in the following:
#Recognize the conditions that present a decay hazard for wood.
#When new construction is planned, protect wood from moisture and decay hazard by proper design.
#For above-ground uses where wood cannot be protected from excessive moisture, use decay-resistant wood, preferably preservative-treated.
#Where wood in permanent structures is in contact with soil, use preservative-treated wood that is approved for ground contact.
#When decay is detected, take corrective action to locate and stop the source of moisture, otherwise decay will only get worse!
#Contact professionals for additional advice and assistance.