I have the calipers removed for brake pad and rotor replacement. After inspecting the calipers, I noticed a lot of wear and tear on the piston seals. Is it worth replacing them? They aren't cheap and it seems slightly difficult to replace them. Is it a concern to leave the bad ones in? Any step by step guides on replacing these? I've read that you use compressed air to remove the pistons.

Thanks.

 

Those first ones look pretty ragged. If they're cracked and no longer sealing, you definitely should replaced them right away. If you can wipe them off and the rubber is pliable and uncracked then they're alright is a good low resolution test.