A closer reading of "Stonewall II" supports my suspicion that this book has had a long production time. The preface mentions the Italian version which obviously came before the German (and the planned but probably canceled Swedish version). However, the clearest hints are a couple of Aagaard's remarks where he refers to the English version of the book which were published in 2001 (and probably written in 2000):
Game 28 (Page 105): "Five years later and a by far stronger player, I must say that today I am less convinced by the advantages of this move."
Game 72 (page 171): "The text move has not been played in any serious game during the last five years, so my annotations from 2000 are still valid".
So my conclusion must be that this book probably was completed some time by the end of 2005. The only indication of a later revision is the preface which is signed by "Jacob Aagaard, Glasgow 2007".
Does this change my generally positive impression of the book?
Well, not that much, actually. A theory book is always best served fresh but it cannot stay up-to-date for very long anyway. It's real worth will always be the ideas and insights it provides - otherwise we would all just be studying databases. And Aagaard's book contains a lot of useful advice for players of most strengths.
The Modern Dutch Stonewall was developed into a mainstream opening by Jussupow, Short, Agdestein and Dolmatov mainly from 1985 to 1995. After that it has had relatively little exposure on the very top level and development has been slow. Finesses are still being discovered but in a mainly strategical opening what was true in 2005 is still mostly true. However, the long production time makes me wonder whether the publishing company, Quality Chess, may have some business problems. Their homepage remains a strange mix of old news and some sporadic recent updates. If that is the case it's a pity because they seemed a worthy challenger on the chess book publishing arena.