The plasticity of our brains

I am getting older. And I have recently gotten aware of a new state of mind. I literary feel how the plasticity of my brain is disappearing. It is a very interesting feeling.
As an undergraduate, when I was taking a class in vector calculus for example, learning about the curl operator in 3-space you were given the definition and you were building a conceptual feeling for what that operator was doing with a vector field. You could actually feel the spatial properties being molded to you head.
This does not happen nearly to the same extent any more. And I think this has to do with me getting old. But it is interesting to speculate in how this plasticity manifests it self. Is playfulness a consequence of this plasticity? And if humans manage to significantly extend our lives, lets say to 500 years or so, I think it will be crucial that we also manage to control brain plasticity. If you only develop significantly during the first 50 years or less, a 500 years life will probably be quite painful.