"As a general rule, most medieval manuscripts are the product of a single scribal campaign. There are of course exceptions, most notably books such as chronicles and cartularies which were sometimes added to over many generations. But the Durham Liber Vitae (Book of Life) is perhaps exceptional in having been updated over a period of some 700 years, from the 1st half of the 9th century to shortly before the dissolution of Durham Cathedral Priory in the 16th century."

http://britishlibrary.typepad.co.uk/digitisedmanuscripts/2013/03/the-durham-book-of-life-online.html