Surprising (well not really... but how shifted is it)
I just picked up a large lot of Ektachrome 100 EPP that expired in 1992 and has indeed shifted magenta but only a little. I was quite surprised.
One brick had been frozen and one brick had been refrigerated.
Once I get some more E6 experience and tighten my process abit I'll compare the 2 bricks and see how much better (if at all) the frozen batch is.

From what little I have read (and it's really highly subjective due to storage,other unknowns) Ektachome may be one of the better films for shelf life.