Whether you love him or hate him, Martin (author of the Game of Thrones series) has some great advice here. Your mind needs to be kept sharp lest it atrophy into a useless pile of mush. This is one of the biggest reasonsI believe that reading is so vital to living. If you aren’t reading and learning then you cease to grow and develop; things that should ideally be done throughout your entire life.
The mind is a great weapon when utilized properly. So why waste it? You would keep your blades sharp with a whetstone, so keep your mind sharp with reading, even if it’s just one newspaper article a day.