Actually, Skj, your work makes a great case for everyone taking all of their very expired Pola film and shipping it to you so that you can do something beautiful with it.
I too am a big fan of old intsnat film and have no issues at all with regularly using 10-20 year old examples with differing results. It's all about expectation and what you're trying to achieve, but there's no question that the stuff
can degrade very quickly to the point where you won't get 'perfect' results. But only very rarely is it totally unuseable. I have a pack of Type 51 that produces nothing, nichts, nada, rien and has been doing so for the last 3 years, but every so often I try out a sheet just in case. I'm stupid like that.