over-the-hill vs overaged

over-the-hill and overaged both are adjectives.

Word	Noun	Adjective	Verb	Adverb
over-the-hill	No	Yes	No	No
overaged	No	Yes	No	No

As adjectives, over-the-hill and overaged are synonyms defined as:

Other synonyms of over-the-hill include overage, superannuated.

over-the-hill (adjective)	overaged (adjective)
too old to be useful	too old to be useful