Heh, I feel like one of Byrne's missteps (assuming I'm remembering this correctly) was that he made the Kents seem pretty old when they found Clark. Superman: the Movie is also guilty of this. I remembered when Smallville first aired, I looked at 40-somethings John Schneider and Annette O'Toole and thought they were way too young to play Jon and Martha when they actually were roughly the right age and other stories probably portrayed them as too old. Maybe it's a veiled Biblical allegory to Elizabeth, making Superman not only Jesus but also John the Baptist.
Nonetheless, I have a latent bias to seeing Jon and Martha nearing their AARP years (regardless of Clark's age), even if it makes little to no sense.