Brake calipers can be rebuilt if needed. Some older brake calipers may be hard to find, and rebuilding them may be the only option. Pistons and rubber parts need to be replaced new, but the rest of the caliper parts don't typically wear out.
The pistons of brake calipers rust over time, and rubber pieces can deteriorate and break. The rest of the calliper should be cleaned thoroughly. The calipers should be rebuilt when brake pads are replaced to avoid loss of pad wear. When replacing the brake pads, be sure that the pads are fitted correctly to the calipers.