Moisture content changes to equilibrium with environment. The rate at which this happens is dependent on how well sealed it is, but as there is permeability, an

Moisture content changes to equilibrium with environment. The rate at which this happens is dependent on how well sealed it is, but as there is permeability, and time, it will happen ;) The only exception is if the wood is transformed in a way that does not enable it to absorb water (or as much of it), such as petrification, etc.