The lifespan of a papyrus roll

A few weeks ago, I wanted to explore a passage in Galen about the lifespan of papyri, as three hundred years.

I recalled this being in L. Reynolds and N.G. Wilson, Scribes and Scholars (3rd edn., Oxford: 1990), but could not find the reference. The Galen passage - 18(2), 630 - is mentioned on page 34, which is not listed s.v. Galen in the Index.

I was pleased to find that Roger Pearse had posted a text and translation of this passage with some discussion and a full translation of the Preface of the Galenic work in question, a commentary on Hippocrates on the workshop of a doctor.