Regarding your argument that past a certain point that maintenance expenses will exceed the value of the car, while I agree for the most part, the question that dogs me is this: will it cost more to replace the car versus the cost of buying, for example, a new set of snow tires (a necessity up here in Ontario). In other words, when I consider the cost of buying another vehicle (cash, meaning that I lose the investment potential of that money*, or I have to sell something, or spend some of my dividends), would it be cheaper and more financially prudent to take the hit of the expense being greater than the value of the car?
In any engineering system, there comes a point where maintenance costs exceed the cost of replacement. repair costs escalate quickly, to the point where replacement is a cheaper and more reliable option than repair. And that is why 99% of automobiles ever made have gone to the crusher.
The problem is, many folks continue down the road of throwing a lot of money at an end-of-life car, AND THEN realize it is costing them a lot of money and throw in the towel and buy a newer car.
It is cheaper to realize when end-of-life is imminent, and then trade or sell before that point.
How can you tell this is happening?
1. Resale value drops to nearly nothing or a pittance of the new car price (e.g., 1/10th).
2. Not many of that year make and model seen on the road anymore.
3. Ironically, many parts become very cheap, as parts makers try to unload their inventory on a shrinking market.
4. You see a lot of the same year, make, and model being junked not for wrecks, but because some major component fails and they aren't worth fixing.5. You don't feel comfortable driving long distances from home.6. Cost of repairs exceeds resale value.
7. When the car no longer meets your needs. Real needs, not imagined ones.