One thing I've noticed as interesting, and this may only be perception, but I used some Tri-X a while ago that expired in 1994. They were processed in Pyrocat-HD and came out with a fair amount of base fog. I gave the film one stop more exposure to overcome some of it, and held back development some. This yielded a better negative.
But the grain was substantially larger than fresh Tri-X, used at an exposure index of 200. Some of that is probably down to the new formulation of Tri-X, but the difference was REALLY tangible. I don't have the scans here to show you (from prints). Now I don't really mind grain, so it didn't really matter, but one thing that made it difficult to live with was that the printing became less intuitive due to the base fog. With crisp and clean negatives I can judge pretty quickly by looking at the negative, what exposure I need in the enlarger to get a decent starting point print. With the base fog ones it was much more difficult, and it threw me off in printing the good ones a little bit too.
I've been using a lot of outdated film and paper in the past, but I think I'm about to turn a corner and start shooting fresh all the time. I'm at a point where I want no surprises, and above all - consistency.
So I've started giving away some photo paper to those that need them, and may start getting rid of some old film stock too, just to be able to focus on my skills more and not have to fight inconsistencies and surprises. It's a two edged sword. I won't be able to shoot as much, but I think quality over quantity will have to prevail.