This is very dependent on location. There are places where, eg, the buildings from the 60s are rather well built, but the later buildings are terrible. It's not the age that matters. My previous apartment was brand new building, but cheaply built to cash in on certain developments nearby (new transport links, new faculty building at the university). I doubt it will still be there in twenty years. My current building is much older but much nicer to live in (thicker walls, better ventilation, no creaks and whistles when the wind blows the wrong way). I think it must be 40 years old or more.

I think it's quite normal to live in a 100+ year old building in a European city center. Though they're usually made from brick and not concrete.

And do people who have built their own house usually demolish it and move on after just 30-40 years? That's when you've just paid off your mortgage, heh.

At my parents' house, they just replaced the roof, which was well over 30 years old. The house itself is over 100 years old and completely fine to live in.

In Europe, people often pay extra to live in buildings which are several hundred years old.