What brand calipers you using?
I have seen factory units get seized up occasionally (oddly enough ever since I moved out to Central Oregon I haven't seen as many as I thought I would with all the snow, ice, and volcanic sand we use up here), but I have seen far more no name autoparts store ones fail quickly after replacement. But yeah, road salt kills a lot of automobile components, I'm surprised that cars last more than a few years with that corrosive stuff on the roads. Also another thing I have noticed is that usually the boots get torn by someone who was too lazy to push the boot out of the way when installing the new pads on a brake job after compressing the pistons (the rubber boots balloon a little sometimes) which causes an entry point for moisture and that lovely road salt slurry. It also doesn't hurt to flush your brake fluid every 3yr/30k in general, but more so if you live in a high moisture area because that stuff is hygroscopic and sucks up water.
Usually what happens out in my area is:
-Customer gets quote from us for factory calipers, has a heart attack and goes to Les Schwab for replacement
-3 months later they come back because their having issues with the brakes
-They get mad at us because their "new" caliper is seized and gets angry with us that they have to buy a factory caliper (or sometimes they go back and get Schwaby calipers a few more times before getting factory ones.)
I do believe Centric and Asin make most of our calipers, so if you find some of their higher-end skus it should be equivalent quality to factory.