One way that people thinking of minds changing over the lifespan is the change in "fluid" and "crystallized" intelligence. Fluid intelligence is your ability to think creatively about abstract ideas and solve new problems. Fluid intelligence is very high in young adulthood and gradually decreases as we age. For this reason, most of the greatest contributions to mathematics were made by mathematicians who were under 35 years old! Crystallized intelligence, on the other hand, refers to facts, vocabulary, and general knowledge about the world. Crystallized intelligence tends to increase steadily across most of the lifespan. That's why people can get better and better at their jobs right up until they retire. For this reason, most of the biggest contributions to philosophy were made by people who were much farther along in their careers, after they had time to read a lot of books and learn a lot of new things!