I had to look it up to make sure, but apparently it's most commonly considered between the ages of 45-65. So, you've still got some room. :)
As for me, I'm heading for the middle of middle age, which I'm sure comes with some magical prize. :) Unfortunately, I've felt like I've been on the downhill for quite a while now, and unlike a real downhill, other than time flying by, I'm not actually getting faster with less effort. :)