Paper capacitors.

[Markpab66]

Hello there, got a question for more knowledgeable members. I've taken the base off my Kit 34 amp, just to check the internal condition of parts, and have discovered 4 paper capacitors. They are Jensen 0.22uf 400v mounted under the tag boards, numbered C11/12/13/14, and they connect the ECF80 tubes to g1 of the EL34's.
My question is, being as they are over 20 years old, and are in a very hot environment, would it be wise to change them for some polypropylene caps, or will it be unnecessary? They look fine, but will need a leg unsoldering to check them properly.
Thanks.