I think most expiration dates are a combination of "planned obsolescence" and cover my ass. The dates are definitely on the conservative side.

Don't know how perishable the contents of the tube are, but probably not that much. I'd say there is a possibility that the active ingredients might lose efficacy in time. I would say any tube that has been opened and have expired, should be thrown away.

Fish, meat and the likes, I avoid going past the expiration date. Other stuff is up to common sense and the good old smell'N'taste test. For medicin, you risk it not helping you the way you hope.