A fridge has to be of acceptable quality, safe, and one of the tests applied is durability - how long would an average consumer expect the product to last?
Fridges are commonly expected to last 6-12 years (ATO, consumer group advice)
Is there a table of warranty lengths by product published by the ACCC? If not it seems like a regulatory nightmare because neither consumers nor manufacturer knows what their rights/obligations are. At least with standard warranties you know what you're getting into.
The price you paid relative to comparable products factors into it - more expensive goods are expected to last longer.
If you and the manufacturer disagree, you can always take it to tribunal to get a decision (and manufacturers never want it to get there so are motivated to resolve your concern before it comes to that).