I've only had mine for about 6,000 miles so far. I learned it had the Nikisil block switched at about 89,000 miles and it has 136,000 now.It shows no signs of which I'm aware of the least indication of any failure.It couldn't have felt or sounded much stronger the day it was installed.It did come with the M-Tech sport suspension and some aftermarket light allow wheels and the leather is in great shape so i paid $9,200.00.Others who've owned the 540 up into that high mileage territory will hopefully be able to put a lifespan to it.I've seen Alusil M60 engines selling for about $6K i think so it may be worth it to pay more for a lower mileage car in better shape if that's possible. The test drive should make you aware of what you're dealing with. Idle should be smooth , steady, no ticking or rapping, no smoke from the tailpipe.Check for fluids under the car where its been parked.I've heard people claim over 200,000 miles of worry free health in these engines.I tend to believe its certainly possible.I have a Chevy V8 In a '99 express van that has over 365,000 now and still putting out lots of horsepower.