I'm 45 and started when I was around 13 and wonder the same thing sometimes. Right now the only thing that makes me feel 90 is the suspension work (ball joints, track rod mounts and such) and it is just my back that feels 90
. The thing that I think will eventually make me get away from messing with cars is my eyesite. I am getting to the point where I have to have alot of bright light to see when turning wrenches anymore. I still find it quite therapeutic right now though.