...you might have to think again. I asked one of my friends from the Microsoft Press team--a gentleman named Ken; he'll be at TechEd Orlando, too--this very question, and he was kind enough to provide an explanation of what goes in to the development of our excellent training kits (TKs):
We plan to make each Training Kit available about four months after an exam goes live. So why aren’t we able to release the book at the same time as the exam?
The reason is that our authors often need solid exam objectives during the writing process, so that the book accurately tracks each and every objective. The objectives are usually in somewhat final shape around the exam beta timeframe, which is usually 2 months before exam live.
The authoring schedule for a typical TK takes 5 months from manuscript start to manuscript all-in. In addition, we then need another 2 months for production, including editorial and tech review, author revisions, build and test of the practice tests, and build and test of the CD. At this point the book goes to the printers where another 4 weeks is required before FCSD (first customer ship date) and the book is available at the distributors.
Books clearly take a long time to do. A good follow up question would be why don’t we start earlier? The reason is that books, unlike the exams and some or our other training materials, are very difficult to change once they’re published. If you pay $60 or $70 retail for a book, you expect something that’s accurate, comprehensive, and will help you pass the exam. So we try very hard to start when the objectives are firm and not release a book until it synchs up well with the live version of the exam.
Another good follow up question would be why don’t we get more authors and reduce the time it takes to write the book? The answer is we’ve tried this and it’s not always true that more cooks make for a better and faster meal. We’ve found there’s often an optimum number of authors on a TK, which makes for a smoother process and a better, more cohesive book.
Still, we try as much as possible to decrease the delta between exam live and book availability, esp. for the more popular exams. For the Vista TS exam 70-620 (“Big Vista”), the book will be available in early May, and the exam just went live January 31 (about a 3 month delta in this case).
Thank you, Ken! Something I like about Ken's answer is the large amount of MS Press lingo you can pick up and use to impress (if you will) people, i.e. "TK", "manuscript all-in", "FCSD", "faster meal". If this smooth talk can't get you a date, you're lost.