How long?

Hmm...good point.
But it wouldn't be the first time that they've invoked that good old Australian rule, the one that says one rule for you and another for us !!

Wouldn't matter probably as reading between the lines it appears they are applying it to individual models, probably using manufacturers specs at time of manufacture and/or a recent test of vehicles of that model. So the fact that an owner keeps his vehicle in tip top condition or runs biodiesel or dieselgas isn't taken into account.