It's a 10-year period not because it's a customer relations exercise, but because they are obligated to do so under Australian Consumer Law. You would normally expect something like a car's dashboard NOT to melt within that 10 year period. In fact, no-one expects their dash to just melt, otherwise it definitely is not fit for purpose and is also a safety hazard. However, having said that, you're past the 10 year cut-off date. So your chances of getting it rectified are now low and there is no longer a legal obligation for Toyota to replace the dash for free.