1
general::
Phrase(s): along in years
Go to up in years.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, on in years. Elderly, old. For example, Grandma's along in years now and doesn't hear too well, or Our dog is not as frisky now that he's getting on in years. This idiom transfers the length of along (and the "onward" of on) to the passage of time. [Late 1800s]
American Heritage Idioms