I would love to know also, mine have torn up two trees already and I have not replaced the second yet. And that was on less than a yr!!
I did find a post that they have not torn up, I had also been thru multiple posts in addition to tearing up the trees, the post is SmartCat Ultimate Cat Scratching Post. They have not torn that up at all, it got great reviews so I tried it and it has been great. They need to make a tree out of the same stuff!! My cats will not use the rope type scratchers, would only use carpet scratchers until I got the SmartCat Ultimate Cat Scratching Post. It took some time to train one of them to use it but I was able to get them to use it.
Good luck!