I "rebuild" all of mine. I think I am still on the original locks from about 4 dozen I bought several years ago. After a catch, I salvage whatever snare cable I can out of them, which usually isn't much. But, I always save my locks. I found I can bargain shop and get 3/32" cable at a good deal if I buy bulk spools. Then I shop around for best buy on aluminum double & single ferrules. I already have a 4-dozen count supply of locks to reuse each year.
Buying the bulk snare cable also allows me to custom make lengths to suit my various set locations and needs, too.
Since you brought this question up, I am assuming that buying, making, or using snares may be a fairly new venture for you??? If so, have fun. Its a great learning tool and I think will make you a better trapper all around. Any time you can make blind sets for specific target species (no lure, bait, calling agents, etc.) I think it makes you a better trapper.
Jim-NE