Keep your BizTalk Schema's Static, otherwise ... BizBalk
[Via Mike Diehl] Hehehe, I like this one! But it's also very true: think about your schema's, get people involved and get them to think about the schema's as well. This will save a lot of time (trust me: been there, dont that).
BizBalk is what Biztalk developers do when someone proposes a change to the schemas.