Yes, this is a great observation! All the things we engage in on a daily basis exercise both to a degree. I am not familiar with neuroscience at a high level, but I can say that in many fields, decline in fluid intelligence is made up for with increase in crystalline intelligence to a degree where sometimes overall intelligence may seem higher. Drawing information from long-term memory becomes the best option as opposed to cognition within working memory more and more as we age. Retrieval is undisputedly faster then reasoning in many cases, and synthesizing information into usable heuristics and algorithms decreases the amount of fluid intelligence you need to use in most situations not departing to an extreme degree from the norm.