Buna-N or Nitrile Orings with R22?

I know the books all say not to, but I am trying to learn why and if I made an error or not.

A quick repair of an R-22 system that was leaking. The service valve both got a new Nitrile Oring. They are now leak free and currently sitting under a test gulp of Nitrogen.

What I don't want is these Orings failing in short order causing more headaches but if they will last a few years, I think the system will be close to ready for replacement by that time. Any thoughts? The service valve body is actually double threaded and the Oring is at the very top. It won't be moving around obviously.

Fastline,
Buna “N” is nitrile.
Ideally Viton or neoprene.

My apology, that is what I meant but I can see how that was confusing. Maybe should have typed as Buna-N/Nitrile

Chloroprene o rings are normally used for R 22 . I believe nitrile may shrink with R 22 . Parker Hannifin make good quality O rings from chloroprene try to contact them for advice to be sure