I'm pretty sure that car engines run with a very large margin of error. I don't know anything at all about engines. I do know that I don't check diddly besides oil and water in any car I have, and I might only get it serviced every decade. Yet they still last for decades. If something sounds weird, I get it checked. Other than that, nada. My conclusion is this: don't get all wound up about what mechanics say. They're trying to make money. Some things are important, like cambelts. Some things are expensive, like head gaskets. Get the cambelt replaced when you buy a used car, and regularly thereafter. Take the car to a mechanic if it's overheating. Drive with the radio off so you can hear the damn thing running and you'll know if you have an issue. Don't stress about the rest. The hood of my car hasn't even been OPEN in three or four years. Aliens could have replaced it with some kind of Tommyknockers style set up for all I know.....
This is terrible, dangerous advice.
If you want to take this advice for "things that make you go" that's fine you're generally only risking inconvenience and financial woes to yourself.
Do NOT take this advice for "things that make you able to control the vehicle". That means brakes, tires, tie rods, ball joints, suspension, etc. Neglect these things and you risk your life and the lives of others around you.
It's not terrible, dangerous advice at all. It's simply saying that you need to keep an eye on your car, including be aware of how it drives and the sounds it makes. If something changes, ask yourself why and do something about it. There are a lot of warning signs before your tyres are so worn they're dangerous, or before your brakes or suspension goes. Why do I need to pay someone to service or inspect it all the time? I'm in it and driving it for an hour or more every single day. If the steering is pulling, or the driving feels weird, or there are any tiny noises or changes, I will notice. I've had a car with a cracked head gasket. I noticed the temperature rising when it wouldn't normally, and took it to a mechanic to find out why. I've had a car with wheel bearings that went. I noticed the sound and took it to a mechanic to find out why. I know how much tread is on my tyres because I clean my car myself and have a look at such things when I'm cleaning. I just recently had a fan belt tightened because the engine made a slight squealing noise.
Seriously, turn the radio off and listen to your car when you drive.
Tell us, what does a nearly rotted through, about to spring a leak as you drive down the highway, coolant hose sound like?
What does acidified/moisture saturated brake fluid sound like as it eats away at your brake hoses and seals and allows rusting of the metal components?
What does a nicely treaded but rotted tire sound like?
What does a malfunctioning ABS sensor sound like (before you need that abs system)?
What does a rotted timing belt sound like?
The advice to "wait until something shows user recognizable symptoms" is foolish. By the time those symptoms show up it's likely that damage has already been done. For example, waiting until your transmissions starts shifting roughly (usually meaning your transmission fluid has degraded) means your transmission has incurred damage because that fluid is no longer preventing metal on metal contact. Or, waiting for your cooling system to start malfunctioning means you are causing damage to your engine block.
Trying to avoid minimal costs of regular, skilled inspections is penny-wise, pound-foolish.
