Here's my personal examples of both sides of the coin with a VT and a VX that have both survived 400,000km:
My son's 1999 VT Olympic clocked up 400,000km a few months ago. He had to do the intake manifold gasket a few months ago, other than that, he's done nothing major. I bought the car a few years ago and my son then selected it from our fleet of neglected Commodores for his 16th birthday. It then sat around for 5 years doing nothing until he passed his licence. I have the
full history of the car, including every single invoice and receipt from the optional extras order form from when the previous owner ordered it new, through every single regular service and even things like the towbar fitting. I'm talking a one inch thick stack of paper. It's not often you buy a used car that has been so meticulously maintained and that has 100% contributed to its longevity. Because of its devoted previous owner and dedicated maintenance it hasn't had anything major go wrong mechanically. My son has, however, put it through a farm fence and taken out a kangaroo, but it is still getting around as a daily driver on its original engine.
My car (2002 VX Berlina) however... I'll be honest, I have a philosophy: cars aren't meant to last forever and full cover RACV membership is less than $25 a month. I love my cars, but I am very hard on them. I wait until something goes wrong and then I turn up the stereo so the sound stops bothering me, until somebody else says "what's wrong with your car? It shouldn't sound like that." and then depending on the effort to benefit ratio, it will
probably get fixed.
I do not have the history on my car and from my experience with purchasing other ex-fleet cars, I strongly suspect this one was a "zero-accountability business car", as in anyone at the workplace who needed to go somewhere drove it, not just one person in particular, so it was treated without much consideration paid to its longevity, because it's hard to prove who caused any problems it developed. These cars are minimally serviced, drive-it-like-you-stole-it, wheelie bins with windows, and yet, somehow, despite a mystery history, almost certain previous abuse and now being owned by
me, it's just clocked up 409,000km and doesn't seem to be in imminent danger of catastrophic failure just yet.