What got me thinking about this was a great line I heard recently, about Queens being the new Brooklyn. That reminded me of a line that comforted me a lot a couple years back, about 60 being the new 30. And that made me think about how Archie Goodwin in the Nero Wolfe books used to refer to women he considered slightly over the hill as "on the shady side of 30." I suspect I'm not alone in finding the 20s the less interesting side of 30, and hardly anybody thinks 35 or even 40 ushers in middle age nowadays. But that doesn't mean I read or write only characters as old as I am.
So writers, how do you choose the age of your protagonists? And readers, what age characters do you like to read about? My protagonist is in his 40s for a number of reasons. I wanted him to have missed Viet Nam but be aware of the Sixties. I wanted him to be old enough to have done many years of hard drinking but young enough to get sober, choose a new career, and start over without committing male menopause. His male sidekick had to be the same age, because they were childhood friends. The female sidekick had to be younger, because I want her biological clock to start ticking loudly a few books down the road.