Thanks to everyone for the replies, they've cleared up a lot of questions that I had.

One final question... Playing as the English, I've just taken Jerusalem, all of Modern France, and everything between Caen and Arhus. I'm planning on taking Oslo, Stockholm, and Helsinki. Are there enough territories left that I can move my focus from Europe to the Middle East, and still get a long campaign victory?

I'll hold ~23-25 territories, plus maybe 3 rebel islands in the Mediteranean. I'd prefer to only fight non-Christians from this point forward if possible. Thoughts?