A Google search turned up a few articles:

Senior citizens who performed as well as younger adults in fluid intelligence tended to share four characteristics in addition to having a college degree and regularly engaging in mental workouts: they exercised frequently; they were socially active, frequently seeing friends and family, volunteering or attending meetings; they were better at remaining calm in the face of stress; and they felt more in control of their lives.

Although there is some controversy and debate on the best ways to improve fluid intelligence, studies are showing a strong link between non-academic pursuits and improved fluid intelligence.

A quick look into some trends:

This report suggests a non-monotonic relationship but maybe a positive correlation between income and percentage of income donated to charity. Unfortunately, this depressingly suggests a negative correlation. (Edit It seems non-monotonic over some intervals but negative overall. Further edit I don't have high confidence either way. Alexander Berger, a research analyst at GiveWell, thinks the piece in The Atlantic is just wrong. I note that some studies are citing "discretionary income" or income with a whole bunch of expenses subtracted out.)

This doesn't seem to list percentages but gives the impression of increasing giving with age. And it's the same story in the UK. Edit This is better:

In 2005, people in the 65-74 years age bracket gave the most dollars to charitable contributions. The people in the 75 years and older age bracket gave the highest portion of income.