We must be the exception, as on our July Western cruise, we didn't get any DVC freebies until my wife went to the DVC desk on Day 2 and told them that we were DVC members (new members, by about two months). We ended up getting some free DVC things (tote bag, etc.), but there was no magnet waiting for us on our door.
Not a big deal, as we had an awesome cruise...but it couldn't hurt to say "hi" to the DVC people at the terminal before you board!