How many top athletes return from their pension to the field and gain their golden age for second time? Not so many.
Remember Michael "Schumi" Schumacher? world seven times Formula 1 championship had his glorious years in 1994-1995, and with Ferrari in 2000-2004. During his pension Schumi worked as consultant for Ferrari, working behind screen.
Unfortunately when he returns in 2010, he cannot compete as strong as he was in Ferrari.
I think this is one sign that skill is perishable, if you dont use it will degraded, and less frequent you used it, you'll become blunt.
Knowledge and skill is transferrable, take example on Keke and Nico Rosberg.
The father (Keke) won 1982 Formula 1 championship and son yaaa quite close to the championship, ignore fact that Mercedes AMG Petronas team in 2012 had many difficulties (source unknown), but Nico Rosberg did won in China (2012), and next year he won in Monaco and Great Britain.
Nico has the ball and skill to race, which I think he had derived from his father, in many qualifying session he got pole position in season 2010-2013, and some said that with that skill he deserve world champion title, nevertheless winning on racing had various factors involved, including team.
Now, get back to our situation, where you had some knowledge and skills to do something good, whether we were born with it or we achieve it from formal education.
When we step out to the job bourse, the real life and then we got an employment that is not suitable to our current skill/knowledge/education background, this gap will deteriorate it, makes us blunt. Then we're left behind, drowned in work routine, busyness and from 8 to 4.
This situation is different when we compare to those work in similar scope as they've studied in college or having skill on it.
These people wont get "early dementia", as they keep apply their knowledge, and even got the chance to develop it further.
My idea is to preserve our brain, our last remaining knowledge, skill and source so it can be applied in some places to create masterpiece or achieve outstanding performance or we can transfer it to others who need it.