I've just done strip tests on two rolls of expired HIE. One 04/2006 and other 08/2008. IIRC both were refrigerated till a few months after expiry date and then frozen (approx -20C)
The conclusion is simple - I cannot tell the negs by looking side by side, base is clear. I probably won't have time to make contact proofs till at least next week so I can't really say if everything is ok but the fact that both look the same (and that 06 was ok last summer) strongly suggests that it indeed is.
Or am I saying something that is well known? I've searched for a while but found some vague statements about expired hie being ok.
That's good to know as I have about 15 rolls left and I want to savour them. Plus I am being more careful in finding worthy subjects for my last rolls...
It is a hit and miss proposition in my experience, and you did keep it in the freezer so the results are good and you are fortunate. I'm very glad.
But, the rule of thumb is that Infra red films die a "heat death" faster than other films. They do not appear to lose IR sensitivity so much as they go into fog. However, the IR dye itself is sensitive to heat and has a limited shelf life in the bottle.
Before I was looking at the test strips against light. But when I've put them on blank sheet of paper I could clearly see that older film has some slight fog when compared to newer. I hope I'll have time to print proofs next week.