Galling is the term used when two surfaces in contact seize up as a result of cold welding. The problem (also known as adhesive wear) is most common in materials such as stainless steel and we come across it occasionally in a stainless rigging screw body* and the stainless stud or fork. To help prevent galling make sure that the two surfaces are clean free from any contamination and my recommendation is a lubricant either Lanocote or Selden Rigging screw oil. Incidentally when mooching round our local boatyard earlier this year I came across these very simple homemade covers for protecting the threads and keeping them clean Some skippers of course leave their mast up when lifting out, me, I prefer my mast to be down and then you get the chance to check everything out, rigging, nav lights, mast head equipment and of course all the fastenings used to hold the fittings in place.
* most good turnbuckles these days either have a chrome plated phosphor bronze body, or if the body is stainless there is a bronze threaded insert both ends