Waening: Never relace a hub to a different lacing pattern. The additional "creases" on the hub flange can cause stress risers, resulting in a broken flange.
On a wheel that I build, I expect to to retrue/ tension a wheel about a month after the initial build. The spokes stretch, and this requires the tension to be restored. The spokes/hipples/crossings etc are all seated when I first build the wheel. The tension drops whether the wheel is ridden or not.
Note also that the tension on the spokes drops when you inflate the tire to 100+ PSI.
dan