My cats love to sit and look out the window--just the right height.  After a while, the carpet begins to come off, especially on the upright posts where the cats claw the most.  I clean it up periodically by trimming the strings and pieces off.  My cats are 7, and we've pretty much gone through the second one.  I've seen scratching posts that have shred much faster.  When the cats use it for what it's for, any scratching post will eventually fall apart.