Homes have a 100+ year service life? Where? I see the median age of housing stock varies heavily in the US. Quickly scanning other markets, I see EU has older housing, in general. Even there, though, they don't talk of 100+ year old houses as being that common.

Scanning websites on this claim, I see that "properly installed, with no damage" some types claim up to 100 years of service for insulation. I strongly suspect that that is a claim that will not hold for the vast majority of homes. More reading also strongly suggests that if your house was built prior to 2005, you probably need to get the insulation redone.

Worse, from my experience, the older the home the less likely you are to have subfloor/walls to actually install insulation. Heaven help you if you do one of those container homes. And if you live in an environment where you have heavy rains or hail, expect damage to creep in rather quickly.

Don't get me wrong, I support the idea that adding insulation is almost certainly a good idea where you can. I just can't bring myself to trust claims of 100 year service life.

Depends on the country. A well-built and properly maintained house in Germany can have a service life of 80 to 100 years or more. Some may even exceed this range, especially those that are regularly updated and renovated.

German building standards contribute to the longevity of residential buildings.

A well built and properly maintained anything can last hundreds of years. Proper maintenance likely involves heavy replacement of parts, mind. And is very contingent on no damage.

I will add I just moved out of a hundred year old house in Seattle. I know they can happen. I also know that house had no air conditioning and retrofitting one on would have basically meant a new house. Even if it looked the same.