Certainly the yeast and probably the clearing agents should be replaced, along with the Kmeta and K-sorbate, bentonite is probably okay, but if you have some already replace that as well.
I would open them, mix them up properly, then give them a taste. If you get oxidized flavors/colors they aren't any good, if not, what do you have to lose??? If they are white wines, I would be more worried than reds, but odds are that after 5 or 6 years they won't be the best thing you ever made.