I think that as long as the car is running fine and has no serious engine/transmission issues, hold onto it.
I'd personally only dump a car when it fits one of these:
1. Unsafe to drive (really bad rust to the point of compromised structure, severe unfixable/crazy-expensive brake problems, etc.)
2. Obvious engine or transmission problems to the point of imminent catastrophic failure. Or engine/transmission catastrophic failure just happened.
3. I realize that it's a stupid car that doesn't properly fit my needs and a different one makes way more sense (if it only would make a little more sense it's probably not worth the switch).
Reason number two just claimed my car. Engine gave out on the highway (200,775 miles). Cost me a rental car to get home, and $100 for the nearby shop to declare it dead.
Reason number two claimed our other car in May. Almost the exact same scenario (182,xxx miles), except I got a Uhaul truck and towed it home myself to declare it dead.
Reason number three was why I dumped my perfectly-fine Volvo wagon in 2014. It was nice, reliable, and had no problems. But it was expensive to maintain due to Swedish parts, and it didn't quite fit our use case (needed a bigger car for certain things, and a smaller car for others).