A car should be bought upon its condition and past maintenance history. Age and mileage doesn't really tell the full story. Seen many low mileage vehicles that had appalling maintenance records, this is especially true for many expensive/premium cars especially it also happens to be owned by an OAP.
It is often the reason why I always say if you don't know much about cars and you're out and about buying a car that is older than 1 year then it is an excellent idea to get a mechanic to give it a once-over before buying. Just make sure the mechanic is a reputable one.
As for how long cars last, we have one Volvo V60 that is now 2 years old and done 470kkm, thus far other than the usual routine maintenance parts nothing other than the power door locks, driver seat motor, the motor that controls the mirrors, turbo bearing, valve cover gasket and just recently the O2 sensor has started acting up. The first 3 items were admittedly quite expensive to replace since the car is no longer under warranty. One thing for sure, I have no shortage of staff asking if it would be sold anytime soon as everyone that asks is expecting it would be let go for a bargain.