[Florin_Andrei]

There's only so many times you can retrain a human. Plus, the "re-trainability" rate decreases dramatically with age.

In a decade or two there will be a heck of a lot of middle-age people hopelessly outpaced by the rate of change. 10 years after that, even young people won't be able to keep up.

[jrapdx3]

While there are age-related declines in certain cognitive abilities, in the absence of conditions like neuro-degenerative disease, it doesn't mean that older individuals are incapable of learning new tasks and skills.

Differences among age groups are greatest comparing people in their 20's vs. 60's (or beyond). Even then, differences are modest.

See this article for more explanation: Clark R, Freedberg M, Hazeltine E, Voss MW. "Are There Age-Related Differences in the Ability to Learn Configural Responses?" http://www.ncbi.nlm.nih.gov/pubmed/26317773

There's also evidence of alterations in "learning style" with age but that's yet another consideration.