These days have phenolic caliper pistons caught up to metal in durability and lifespan?

 

Not IMO.The Phenolic pistons are easily damaged and more prone to seizing in their bore than the metal ones.The metal ones can last much longer and will not crack or fracture as the Phenolic pistons will when they are removed.

 

Phenolic were all that were available at Rock Auto for a 1996 XJ. Dumped them and thought I found real metal ones at NAPA, because the photo shows a metal piston. No dice: https://www.napaonline.com/en/p/UBP85392S?ref=Mg==
Summit does not reveal the material, but one comment on one brand mentions they are made of "composite material". 1996 JEEP CHEROKEE OMIX-ADA Disc Brake Caliper Seal Kits 16747.04

Here is to hoping that between four calipers I have two good metal pistons.

 

O'Reilly claims these are steel, even though the photo shows composite.
https://www.oreillyauto.com/detail/b...cherokee?pos=0