I know you've probably heard it before but it really is a good practice to get into. You should always loosen your bow adjuster everytime you're done playing. Those of you with real wood bows should especially pay attention since keeping your bow tightened will eventually take the bow out of the stick leaving you with a virtually unplayable bow. Leaving your bow tight also puts excess pressure on the soft brass eyelet that your adjuster screws into. This can cause the threads in the soft brass to strip out leaving you with no adjustability at all.
If you've purchased a nice instrument do yourself a favor and pay attention to humidity levels. there is nothing worse than discovering that a seam or glue joint has opened up due to excessive dryness or that your top or back have a split in the wood due to the wood shrinking. There are violin cases now with guages that show you humidity levels so you always know how dry things are getting. This way you can take steps to ensure proper humidity levels before it gets out of hand.