Nothing wrong with using old gear. A lot of my gear is pretty old. I never seem to find one year old gear thrown away, but I will keep looking.
I do see the local shop unload the heavily used rental/training gear for a little more than they paid for it each year however.
That is pretty interesting, that they could actually sell gear for more than they paid for it. Of course you don't actually own the local dive shop, nor do you actually do their books. So, like Paul Harvey says, there is always more to this story.