All but a very small percentage of sailboats (the trailerables) leave the mast up all of the time. I've had boats for years which sit on trailers with the mast up and have never had damage to the rig or the hull. In fact, you could make a pretty good argument that the boats stored in the water pass more wear and tear onto the rigging from the wakes and constant water movement than windage to the rig passes on to the hull. Every time I have visited parts of the world where water freezes they simply dry dock the boat just as it came out of the water. You can imagine the cost if every sailboat had to drop it's mast for winter. If it makes you feel better, drop the mast, but if you have a good reason to leave it up be assured all will be well when spring comes.