Well, I'm in my 40s, bike commute, recycle, yadda yadda, but honestly, we could all be wearing hair shirts and living in caves without it making the slightest dent in statistics. As a self-selecting group of cycling enthusiasts TE'ers are not representative of the general public, especially not when it comes to transportation choices.

As to whether people in their 40s and 50s in general live a less sustainable lifestyle than younger people - I suspect that statistics would show that that's correct, but also highly variable.