It is a double-spreader, complicated rig with rod rigging and IMHO there is more chance of damaging the rig in the process of removing and replacing it every year than simply leaving it in place. In fact I got a slight kink last time they re-stepped it after I had replaced the rod. Plus, it saves a few hundred $. Most of the larger boats in the yard where I store my boat leave their masts in.

For a simpler mast with wire shrouds I agree taking it down every year probably makes sense. We always did on my dad's boat (Majek).

I have devised a covering system which (almost) completely keeps the water out. I'll try to post a pic later this fall. Briefly, I remove all the stanchions and the bow pulpit. I have a pair of 2 x 10s with a slit cut in one end. The 2 x 10s lean against either side of the mast at boom height and extend to the toe rail on either side, with the shrouds running through the slit (I am fortunate in that the shrouds are all in a line athwartship, attached to a common base). I attach the spinnaker pole to the mast (at about the height of the boom) and the forward end sits on the deck at the bow. Some PVC tubes spaced every 3 feet are held in place with light line and are mounted at right angles to the pole (in other words they extend aft a bit as they go from the pole to the toe rail). This creates a nearly flat frame over which a tarp can be pulled taught without any craters to catch water. The aft end of the tarp is held in place with a piece of strapping fastened to the 2 x 10s.

Aft of the mast, I have pairs of 2 x 3s spaced every 2 feet. Each pair is joined with a metal hinge on the lower side, which makes them very simple to put up and take down each year. A piece of PVC pipe runs aft from the mast and forms the 'ridgepole.' It is a few inches higher than the boom. The PVC pipe has a series of holes; I screw a carriage bolt from the inside surface of the pipe into the end of the 2 x 3 (adjacent to the hinge). This makes the entire structure quite rigid. I have a large tarp made of Griffolyn from Reef Industries. The forward end is screwed into the athwartship 2 x 10, and lines run under the boat to hold it in place. I have a small tarp at the aft end which serves as access. It takes about 4 hours to erect and 2 to take down every year. I've found that removing the stanchions and pulpit makes it A LOT easier to cover the boat, and it gives you a steeper 'roof'. The main thing is to keep surfaces taught and flat so you don't get any craters.

I have more respect for technical engineering writers after trying to describe the above

Max