You're pretty safe as far as "shrinkage" goes I think. Lumber still "moves" during "seasonal" changes in heating and cooling (and at times for other unforseen reasons such as settling). I still recommend using adhesive. If you have a wall in your house that you know is not glued, bang on it with the heel of your fist. You can hear the board "rattle" against the studs (interior non-insulated wall). The same wall with glue won't do that. If you ever have to patch a wall that has been glued, when you tear out the piece to be patched, the backing paper on the rock will still be on the stud when you pull the damaged piece out. The likelyhood of "seasonal" lumber movement causing fasteners to "pop" is greatly diminished with adhesive....