I'm sitting in a meeting where we're discussing consolidating KB articles, and one of the issues that's come up is that most times when we go to consolidate two or three or fifteen KB articles into one, we end up with a 20 page KB article that's really a white paper. The KB team usually tries to keep KBs to two or three pages.
My personal opinion is that long KBs are just fine, the more information the better, assuming of course that the search actually works to get you the results you want (and if the search on support.microsoft.com doesn't, then use whatever search engine you prefer with a +site:support.microsoft.com, for example). Since the content in whitepapers isn't searchable today, I prefer having it in the KBs which you can search from one place.
But since I might be biased, I wanted to ask the question in public: Is it OK for KB articles to be really long? Or is there a length after which it ceases to become useful?
Add any feedback as a comment to this post and I'll roll it up and present it to the KB folks. Even if the consensus is different from my personal opinion, I promise I'll still give the feedback :-)