I believe the existing warheads all use plutonium that is well past its original rated service life, but have allowed to remain in service based on updated understandings of the plutonium's rated lifespan, which may, or may not, be coming to an end.

Pretty sure Los Alamos just manufactured the first plutonium pit since the end of the Cold war.

Edit - found a source:

https://thebulletin.org/2024/10/the-energy-department-just-made-one-plutonium-pit-making-more-is-uncertain/