Writer: Cary Bates, Bob H. Rozakis
Artist: Curt Douglas Swan, Denys Cowan and various
Publisher: DC Comics (1980-982)
Includes: Superman (backstory) #354, 355, 357, 361, 364, 368, 372 and The Superman Family #200
These backup stories in the Superman comic had Superman aged in real time. The stories are about the grandson of the original Superman taking up the mantle in 2020. It's just cool to have three generations of Supermen in a story.
I have always thought the comic-verse of DC and Marvel should have their characters age in real time. If the characters get too old then you can introduce a new universe of younger characters; much in the way they did with Earth 1 and 2 at DC.