I'm cheap and only play blackjack, so nobody gives me nothin'! (except room offers from El Cortez...lol)
However, my parents, gambling away my siblings and my potential inheritance , are Diamond members at Harrahs and have been for years. I know my dad has made several comments about "gotta go play some to get my Diamond level" as the year winds down. He seems to know how much he needs to play/get in order to make that next level. (just like me with my Choice Awards card for free hotel stays)
They get lots of free room offers but the bennie my dad likes the most is the "secret" room they have for Diamond level people. (at least at some of the Harrah's, don't know if they all have one) There are always free munchies and free drinks available...and let me tell you, the drinks are NOT watered down as they often are on the floor. DonDiego and I have been to "the room" several times with them as guests, and after a couple of strong Long Island's DonDiego needs to help me walk a straight line to our room! lol.
In response to your question, based on what my dad has said, I think if you are a Diamond you get Diamond offers for the entire year and then everything resets in January and you have to 'earn' your Diamond status again the next year. If that is the case, then not using the card should not hurt your offers for the current year. I know my parents get offers all year long even when they haven't been gambling for a while.
Anyway, I agree with everyone else, Ledhead. Use your card everytime you do any gambling. It doesn't hurt and it may help so, what the hey!
Another thing to check is how each casino deals with duplicate cards vs 'couple cards'. For instance, some casinos don't allow the same card to be played in different places at the same time and some do. Some casinos put a married couple's account as a group for benefits, but some casinos keep everything separate. If I get 500 pts and DonDiego gets 500 pts...we'd get better offers if that is grouped as 1000 pts. So we always try to do that if possible. Maybe someone else in your party could have a duplicate card and get pts for you if they don't care about pts for themselves.
At any rate, enjoy your Vegas trip.