Just the obvious: all fluids exchanged regularly; spark plugs and ignition coils every 80,000 or so. At 18 + years old, I'd certainly have a backup warming up in the bullpen. I think the worst error car owners make is not knowing what comes next when their car suffers a catastrophic breakdown or gets totaled.
Live it up: There will be plenty of time to be old when you die.
* '09 Vibe: 1.8 liter *
* '10 Hyundai Elantra Touring *
* '07 Honda Fit Sport *
On Deck: '22 Tucson or Sportage/'22 Subaru Crosstrek/'22 Corolla Cross