> If you're 43, you should know what you want to do. In a word, no. You can change what you want to do at any age. At 29, I chose to put academia behind me t

> If you're 43, you should know what you want to do. In a word, no. You can change what you want to do at any age. At 29, I chose to put academia behind me to "go industrial". At 37 I started my own company. At 51, I joined another company. And again at 53. You might have a general idea of what you want to do at some age, or something very specific. A particular itch you wish to scratch (see my 37 year old self wanting to prove that I could do "it" better than some of my predecessors). Today, my 54 year old self wants to continue to enjoy working with very smart people, on hard projects, making material impacts upon top line and bottom lines of larger companies. In a real sense, my employer, those who actually pay my wages, changed 6 days ago. In all these transitions, I've altered what I did, what I wanted to focus upon. You shouldn't be scared of being old. Age is, for the most part, only a number. It is not relevant, unless you wish it to be. Or deal with some idiotic companies that think it is important. You retire when you want. A friend 10 years my junior retired 2 years ago. He's bored silly now, but still, you can choose what to do, when you want to do it, modulo physical/health issues. For me, I think I realized I couldn't keep going at the powerlifter rate in the gym after I hit 53. I had to leave weights for the younguns to lift :D