Decks, Patios, Porches and Docks - Trimming treated landscape timbers

We are redoing a small retaining wall around our concrete enclosed well. We are using treated landscape timbers. Yes, we are aware of their shortcomings, but they are the most economical materials for our budget, and we are making sure they are well secured to minimize warping. My question is, can the timbers be trimmed. I would like the wall (only four timbers high on the tallest side) to be set in a couple inches with each row, rather than each tier being right on top of the preceeding row. My husband says the treatment only penetrates an inch or so into the wood, and if the ends are trimmed the timbers will rot sooner. Thanks for your help!

It's true that the treatment doesn't penetrate completely.
You can buy a gallon of (...hmmm Cuprinol?) or similar, paint it on the cut ends multiple times to get it into the wood or let the cut ends soak in a bucket of it overnight. Not Thompsons or one of the cheap deck protectors.

Any good hardware/paint store should have a similar product.
Big Box stores may carry it, but you may have a problem finding someone who knows where it is and what its for.

Again, it's a specific product for wood in ground contact to protect against rot and insect damage, not a waterproofing deck coating.