Well...I'm going to be 32 this year, and have been doing MT since I was in middle school. Nothing to be seen in terms of permanent injuries yet!
Of course...I wonder how the shins will old up when I'm 50...
"I don't know if anyone is known with the art of "sitting on your couch" here, but in my eyes it is also to be a martial art.
It is the art of avoiding dangerous situations. It helps you to avoid a dangerous situation by not actually being there. So lets say there is a dangerous situation going on somewhere other than your couch. You are safely seated on your couch so you have in a nutshell "difused" the situation."