Life expectancy of an old building apartment?

Panel buildings are properly renovated and expanded here. Afterwards, they are again top quality and externally quite okay. With color accents, balconies, and sometimes different roof shapes, they hardly have anything to do with the gray housing estates of the past. Where there is no demand for apartments, they are surely also demolished, but for economic reasons.

It really depends on the construction method and how the house is maintained. What kind of building is it exactly?

A major drawback of the prefabricated building is the original interior mini wet cell. Otherwise, as already writes, you can definitely make something out of it.

By the way, the oldest roof in the world is more than 5000 years old and still waterproof. Admittedly, however, it is not a residential building.

The initial question is hardly answerable exhaustively. Too many constraints.

A major drawback of the prefabricated building is the original interior mini-bathroom.

The prefabricated building never existed as a single type, but rather a whole family of systems, each with several floor plan variants, by no means only with interior bathrooms. The prefabricated apartments are even mostly found in medium-sized multi-family buildings (two- and three-unit buildings), while the interior bathroom is more the domain of large point blocks. It is astonishing that thirty years after reunification, the notion still persists that the former GDR was a third world country.