According to Caran d'Ache, it is about 600 A4 pages written in full. As far as I know, it used to be called 6 kilometres, which should be about the same.
(Assumption: 30 lines at 18cm, characters result in about double the distance. This results in around 10 metres per page).

By the way: I have been writing with this type of pencil lead for over 40 years and can highly recommend it. As a left-hander, I appreciate the fact that it doesn't smudge.

About 500 metres - if you write really fast you can even manage 600 metres.