Disc brake caliper repair

When replacing brake pads, should the calipers be repaired (new discs & O rings) if there had been no prior indication of sticking or hanging up?

No. Just make sure the caliper pistons compress smoothly back into their bores. And then clean/lube the caliper slides.

Tester

If they are working perfectly fine then just clean/lube slides. DO NOT USE WD40