Maybe the old saying is true. Recent studies mentioned in a New York Times article suggest that those "senior moments" may not be due to failing mental capacity, but rather to a broadening attention span that requires more thought processing as we age.

These findings don't minimize the sometimes negative impacts of aging upon mental capacity, as found in Altzheimer's Disease, for instance, but suggest that the effects of aging upon thinking are often oversimplified and misunderstood. 

According to an article at WebMD, two recently published sociological studies have concluded that older Americans are generally more content and satisfied with their lives than their younger counterparts. Also, older adults tend to be more socially interconnected than younger ones, a factor which researchers believe is related to their greater happiness. The studies suggest that stereotypes of seniors as lonely individuals wasting away in misery are flat out wrong. For instance, about 50% of 80 year olds reported being very happy, compared with about 24% of 18 to 20 year olds. The least-happy group? Baby boomers.