The first thing that many people don't understand is the difference between repair and maintenance.
A non-inclusive list of maintenance items that all cars need done on a routine basis....
Brakes, exhaust, shocks/struts, tires, oil changes, filter replacement, transmission flush and refill, lubed, clutch replacement, timing belt replacement (when applicable, some cars do have timing chains, which don't routinely need replaced as much.), and to a smaller extent, head gasket replacement.
Sometimes you can judge a vehicle by the timing necessary for the replacement of these maintenance items. Example is, I've driven nothing but Japanese exclusively since 1995. Never have I touched brake rotors and I have always replaced brake pads about every 50k miles. Now with the Ford, not only are the pads replaced every 30k miles, but also the rotors.
I've always bought used except for 1992 when Mom talked me into buying a new car and 2007 when I decided to buy new for my wife. Both times I should have bought used and bought better. My list is....
1990-1992 - 1985 Ford Escort - 46,000-86,000 - Junked
1992-1995 - 1992 Geo Storm - 25-60,000 - Traded, was a POS
1995-1996 - 1989 Toyota Pickup - 94,000-135,000 - Totaled in accident
1996-1996 - 1994 Toyota 4Runner - 54,000-62,000 - Owned 6 months, couldn't afford
1996-2002 - 1988 Toyota 4Runner - 105,000-189,000 - Traded up
1997-1998 - 1992 Chevy Corsica - unknown-134,000 - Wife's when we got married
1998-2010 - 1994 Nissan Altima - 48,000-169,000 - Traded up
2002-2007 - 1999 Toyota Tacoma - 52,000-98,000 - Missed Toyota buying back for frame rust, traded
2007-current - 2006 Mazda Tribute - 900-100,500 - bought leftover, still driving. POS
2010-2010 - 1994 Honda Civic - 172,000 - 179,000 - Paid nothing, put a new head gasket in, and sold it.
2010-current - 2003 VW Jetta 1.8T - 74,000-101,500 - Love this car
Of the cars I've owned, The Geo (Chevy import with Chevy parts on it), Ford Escort, and Chevy Corsica I've gotten rid of because of constant mechanical problems. It wasn't until I started buying Toyotas that I never had another repair or unreasonably short life for maintenance. I didn't put a dime into 5 Japanese vehicles for repair. I put a clutch in the 88 4Runner, expected maintenance, and put a head gasket in the Honda because that is how I aquired it (pretty common maintenance for the Honda 1.6 ltr motor.) The highest mileage 3 cars all were traded due to rust problems with the higher miles. I fix the rust, but it eventually gets tiresome fixing it year after year. Around here, you are pretty much looking at rust problems starting any time after 150k miles with the salt on the roads.
Because of needing maintenance in 4 times quicker period of time, the Mazda Tribute (Same as a Ford Escape) has cost me in 100,000 miles, more money than the previous 6 Japanese cars I've owned with combined 406,975 miles on them.
Mileage doesn't matter, age doesn't matter. What matters the most I have found when trying to determine how long to keep a car is, what car is it and who is the manufacture?