I am in a bit of a pickle and I am looking for help on how to communicate my feelings.
I have an awesome neighbor couple next door who have known me all my life. They love to go on trips and bring back local goodies in exchange for me keeping an eye on their home while they are gone. They usually give me jams and pancake mixes etc. - gift basket stuff that I can donate or regift if I don't use it all or it isn't to my taste. I've always been happy they think of me, but now they've upped their gifting and I don't know what to do.
They have started sending me specialty desserts from those gourmet magazines that come in the mail. For Thanksgiving they sent me and my 3 brothers a cheesecake sampler. It came in a big Styrofoam box (dry ice etc.) for protection, which was very hard to get rid of since I try to be earth friendly and my trash can is small for economic reasons.

Now today I got another box from them - a huge cake. I remember it from last year - it is too rich and sweet and the four of us will not make a dent in it! Since the company sends their catalog with the food, I looked up the cake because I didn't know what flavor it was from looking at the outside - unfortunately now I also know how much they spent on it - I wish they had saved their money!

Or, if they were willing to spend that much on us, given us a practical gift card.

So to sum up: I feel it is a waste of money and food for them to keep giving me and my brothers these decadent desserts. I am touched and grateful for their generosity, but their goodwill is coming in the form of a terribly impractical gift. If we loved it and ate it all maybe it wouldn't matter as much, but it is on my conscience that they spend so much on food we can't finish (or don't even really like). Since it is perishable it can't be accepted graciously and regifted.
When I call or write to thank them, how can I say "Thank you for the gift" while tactfully steering them away from giving us similar gifts when the next major holiday comes? I don't want to hurt their feelings and appear ungrateful, but I don't think they would send us the desserts if they knew we weren't crazy about them. I'm afraid maybe we were "too" thankful last year and they mistook our polite enthusiasm for a desire to receive these desserts regularly. I want to be nice without digging myself any deeper. Any ideas about what I can say about the desserts to give my neighbors a neutral reason not to send them? I've thought about saying I'm going gluten free but I don't want to lie and that would just put the pressure of eating the desserts on my bros.

I'd honestly take a plate of homemade cookies over an overpriced store bought cake any day...
Help?