I think there should be no age limit during learning new things. As long as he is performing the task willingly and finds interest during the journey it will be okay for me. I'm 41years old and just started to learn English. The whole learning process makes me enthusiastic because throughout the journey I have made many good friends from different countries. It makes me happy to talk with them. I have also came to know much amazing and exciting stuff through them. So, In my opinion, everyone should learn something new whenever they got time.