The Skelton structure will last YEARS! The needles will fall off in a year or so. But the limbs and branches will be there a long time. You will be loosing hooks and bobbers for years to come on them.
The trick is to put them out where they CANNOT be found by others. I would not put anything on them that would make them show up on depth finders. I'd put them where I knew they are and not tell a soul.