All the timber you receive is still subject to change.  The cell structure of the timber is constantly reacting to the environment around it, regardless of if it is coated or not.  When it is hot and humid or wet it will grow.  When it is cold and dry, or no humidity in the air it will shrink.  Even timber on 100yr old buildings is still moving.  They are constructed to allow for this movement, and so should your project.