voor alle veertigers (en vijftigers, zestigers, ...)

Die ersten vierzig Jahre unseres Lebens liefern den Text, die folgenden dreißig den Kommentar dazu.

-Arthur Schopenhauer, 1851-

The first forty years of life furnish the text. whereas the following thirty supply the commentary.

-translation E.F.J. Payne, 1974-

Given this was written in the 19th century and by now life expentancy has increased, I think we can either adapt the quote to:

The first forty years of life furnish the text, whereas the following forty supply the commentary.

or we expand the quote:

The first forty years of life furnish the text, whereas the following thirty supply the commentary, and the next ten provide the conclusion.