I have a question about the 1928 neoprene buffers

[jpw43]

Do they have a shelf life? If not I think I'll buy a couple of PK's to have on hand.

[Rekraps]

2 hours ago, jpw43 said:

Do they have a shelf life? If not I think I'll buy a couple of PK's to have on hand.

As long as they remain pliable. 

[Doug Quaid]

Neoprene is a kind of synthetic rubber that is black colored.  

Polyurethane is a resin that is translucent.

Most plastics have a limited shelf life.  If you look up the shelf life for various gaskets, it's usually 5 to 10 years, can be as short as 3 years.

I wouldn't worry about the buffer hardening over time.    If you consider that the original bakelite Thompson buffer is as hard as a piece of gravel, you can probably use an old polyurethane buffer until it starts cracking apart. 

They probably used bakelite for the buffer because rubber did not hold up to the pounding and in 1919 pretty much the only plastic available was thermoset formaldehyde resin.

Taking a guess, to be conservative figure on a 10 year lifespan.