The ATO defines the effective life of a depreciating asset is how long it can be used by any entity for a taxable purpose, or for the purpose of producing exempt income or non-assessable non-exempt income
- having regard to the wear and tear you reasonably expect from your expected circumstances of use,
- assuming that it will be maintained in reasonably good order and condition, and
- having regard to the period within which it is likely to be scrapped, sold for no more than scrap value or abandoned. (www.ato.gov.au)