Just to spout off, here’s the thing, while it is generally cheaper to keep a car going for a longer period of time, at some point everyone has to buy a different car. Some buy sooner than others, but repairing a car is only delaying the inevitable need to replace it at some point. So outside of the personal considerations like comfort, looks, dependability, there is the cost and obsolescence to consider. If you pay for a repair, you should just expect to be able to drive the car X number of miles to get the cost per mile of that particular repair down to a reasonable level. For example, If you put a set of tires on for $600, you should at least expect to get 20 or 30,000 miles out of them to get part of your money back. If not, why do it? If you put a $3000 transmission in, you’d better hope to get at least another 50,000 miles out of it.
At any rate I like to look at the average cost per year of anything, and compare that to the average lifetime cost per year of something newer. Whether lawn mowers, refrigerators, washers, etc. they all will need to be replaced at some point in the future so it may be meaningless from an average cost per year standpoint to “try to get another year out of it”. Then you’ve got the whole obsolescence problem with crush zones, air bags, electronics, parts availability and so on, that might make keeping an old car, even if no problems, undesirable. Easy for me to spend someone else’s money, but I’ve kept cars going for half a million miles when I should have dumped them at 300,000.