Green Lantern Hal Jordan was 23 when we got the power ring from Abin Sur. While even he was rebooted many times to keep him in that 20s-30s age range, there were a couple of decades of real passage of time when they allowed him to age into his 50s and 60s including gray hair:
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Bruce Wayne was an old man in The Dark Knight returns. There's even the Batman Beyond storyline that is a old Bruce Wayne coaching a new younger man to be batman.
The Justice Society has golden age heroes with natural aging making them senior citizens.