old age, age-old

Old age or old age means the retirement years; the years after age 65 --
He's saving money for his old age.
We have to eat healthy food now so that we won't be decrepit in our old age.

Age-old or age-old means traditional, or from time immemorial --
No one knows the origin of these age-old customs.
The yule log is an age-old practice, still common in rural areas.

Now that you know that, you can say --
"In his old age, he liked to remember some of the age-old things his parents had taught him about the land, and how to care for it."

Note--"old adage" means an old saying or proverb --
He can quote an old adage for every situation.