Wiktionary
middle youth
n. A period in life where one can not be described as young, but does not consider or wish to be considered middle-aged.
Usage examples of "middle youth".
He nodded, a stocky man with his peaked cap set conservatively straight, a man without imagination but with a sense of responsibility, too old now to be stirred by the rumours of a fight for freedom in tomorrow's streets, a stolid man prepared to weather the strictures of a regime he'd come to accept since middle youth, a man to whom I didn't say the police are looking for me, let me through quickly in the cause of Sroda.