In the current comics they're working on a five year timeline with most heroes' careers beginning around 2009. I'm gonna use suspension of disbelief and say it was closer to 2005 when heroes became active. Superman was around 25 ish when he introduced himself to the world... 15 years later in 2020 he's 40 but just looks like a graying 25 year old. Batman was closer to 30 so now he's roughly 45. Most adult heroes were between 25 and 35... Hawkman was around 32 in my mind when he was acting as a hero in 2005 so he's 47 and a little more worn than the others....

~KL~