Generally with expired Endura, it's a yellowish cast to the whites, as PE mentions. Cut sheet endura is still good even several years out of date. I'd say less than 5 years out is nothing to worry about, and you'd only notice the yellow cast if you have fresh paper to compare with. Freezing can help extend it even further. Beyond that it gets a bit more noticable but still usable. I used some that had been stored poorly (by me), in hot attics and whatnot, since 1993 (!!), Supra II. It was heavily yellow cast, so much that I couldn't correct it enough to get it neutral, but it still gave a semi-decent print, just not really color correct, and contrast seemed lower than it should have been. But it still printed! amazing.