I've had more than a few older cars, and what I tend to find is that there are basically two extremes of people who own them; the "fix it one piece at a time as it breaks" and the "never fix it, just run it until it can't run anymore." Seems like nobody believes in preventive maintenance. Since I prefer to do the labor myself whenever possible, and I'd rather do it at a time and place of my choosing than on the side of a highway a couple hundred miles from home, I tend to replace entire sections of parts when one breaks; basically, whatever has to be removed in order to get to the part that I need, or whatever requires removing that part to get to, if any of those are reasonably expected to fail in the next 1-2 years.
It makes some cheap repairs cost more at the moment, but in the long run, it's cheaper than payments on a new car. I think the most I've spent in a single month on the last 2-3 cars was about $450. My running joke on the Saturn was that if I put $400/mo into it, I'd run out of non-cosmetic stuff to replace in about a year, and have to start buying body panels; even a professionally rebuilt engine/transmission/differential bought as a unit was only $1200 from one place, and pulled as-is to rebuild myself could be had for $500 or less.