Summers over, the martins are all gone south for the winter, now what do I do with the gourds?
Just like any other natural items in nature, gourds will deteriorate if left out in the elements. Therefore, to protect them, they should be put away in storage for the winter months. This one action alone will help make your gourds last many years to come. You've put a lot of work into preparing them, you might as well go that extra step and try to protect them and make them last.
This is the easiest way I've found to 'put them up' for the winter. After taking them down and cleaning them out, I get some of those large, 30 gal heavy duty trash bags. I've found the real thick ones work best. I then place about 6 to 8 gourds in each one and then seal it tight. I happen to have a storage room over my shop, and I hang the bags of gourds from the rafters so the insects and rodents can't get at them. The ones I use have their own draw strings, so it makes it easy for me to hang them plus, I can re-use them each year. The plastic bags are very slippery and makes it just about impossible for anything to get a good foothold without sliding off. Any spare, out of the way space will work if you don't have a shop like me. An attic, a wall of a garage, back porch, or storage shed, etc. You just want to get them out of the elements and out of your way until they are needed next spring. Just make sure the place selected is dry and that the bags are sealed tightly so nothing can get in.
Leaving them hang out in the elements all winter is not a good thing to do with them, and their usable life will be cut very short. And just bundling them together and setting them in a corner somewhere without protection is inviting all kinds of creatures to take up residence in them. You'd be surprised at just how many nests one field mouse can build and how many holes they can chew to get to them. Take the extra measure to protect them. Believe me, it's worth every bit of the effort.