One thing that I've heard a lot over the years is that those working in the IT world generally don't make life time careers out of it, but tend to "burn out" and start a new career doing something else unrelated (e.g. going from software development to being an accountant).

Have you found this to be generally true in your experience and if so, what is the general impression on how long people work as developers before starting a new career?

I've been in software development all my working life from junior developer, through senior developer to team lead/manager and now back developing (though hoping to get back into management sooner rather than later).
My working life is now nearly 40 years and in that time I've changed domains and technologies as the companies I've worked for have changed. I've then used that new experience to find new positions when I've had to, which has in turn led to other new domains and technologies.
All that time I've known developers as old or older than me.
I think "burn out" happens if you try to do too much - working 12+ hour days and/or weekends for extended periods and happens in any industry not just computing. I know that if I had to do that I'd be looking for something less stressful to do.
If you find a working style that fits your temperament then there's no reason why you can't continue working until you retire at 65 (or when ever).
