"Overall Half-Life 3 or Half-Life 2 The Episodes or whatever you want to call this ended up coming about more quickly than six years, so I think that some of the things we projected at the first - the name, the time-length of releases - we were pretty off on, but the idea was that this development would produce better games faster and we´d be happier and gamers would be happier"
source :
http://www.eurogamer.net/article.php?article_id=76582&page=1