There are 4 basic reasons people came in to purchase a car.
Current car is messy: I sold a ton of cars to people who’s current car they hated simply because it was dirty. Some elbow grease or paying for a good detail could have saved them $20k.
Wanted new technology: I sold $50k cars weekly because of Bluetooth capabilities. No matter how old your car is, you can add this to any existing car for around $200. Cheaper if your DIY.
Wanted it as a status symbol: Cars always look amazing at a dealership where they are waxed, clean, and smothered in Armor All and tire shine. In two weeks the difference between your old car and your new car will probably be negligible. The whole status symbol thing really only lasts a few weeks. Most of your peers don’t know the difference between a new and much older models if they are both dirty.
Mechanical problems: This is the only reason I would advise anyone to purchase a car. Eventually the repairs get to the point where its more expensive to keep it than to move on. If you are buying a car for any other reason than this… don’t!
Safety isn’t something I mentioned before, but probably should have. Regardless of how reliable a car is, if you are driving something with a rusted frame and 20 year old safety features its time to upgrade (assuming you can afford it). My wife and kids drive in a 5 star crash rating car with every modern safety feature. We have chose to be stingy in other places in our finances so we can afford to have a car with these types of features. Its worth a little bit of money to us to know our family is safe and to be able to see when backing out of the driveway.
That moment when repairs out way the cost of upgrading is tricky. I have been burned several times by spending money on repairs that I thought were a good investment only to have more and more repairs pile up. I wish I knew some perfect rule for this. I don’t. I have repaired cars I shouldn’t have and I have gotten rid of cars that probably would have been great with minor investments.