Switch to another technology, at least once in 10 years. It doesn’t matter what you think about the software language you use, it’s a fact that software changes. Anyway, if you were good, you can always switch back. On the other hand, if you only know one language, you might find yourself trying to speak French, just because it was there before.
This is a good article. Working in technology is tough because everything constantly changes. As we get older its natural to become more change averse. But if you work in a field that is build around supporting change, you have to keep fighting entropy.
In a lot of ways being a bit older (Yes, I am over 40) has helped me be a better System Architect. In the main, I've learned how to deal with people and personalities. I've learned how to deal with my own personality as well, and when I have to pause for a moment before I speak.
I have also learned more about the business areas I support, and how their bottom line can be effected by IT.
Knowing a little bit about many different systems and tools helps me as well. From my varied experience I can extrapolate methods to work with new tools. I have developed troubleshooting techniques (and talent!) that make me one of the better analysts out there.
Age discrimination is real and it is out there. My last job.... well lets sufice to say that when the layoffs went down, those with the most years with the company were more likely to be cut. Last in first out was not practiced in any way shape or form. I think it was more a case of salary discrimination than pure ageism. My suspicion is that that wanted to pare down more highly compensated folks and then hire new hires that would do the job cheaper.
What they may not have realized... there is a wealth of organizational knowledge in the workers who have been with your company the longest. And nothing kills morale faster than seeing the people you have looked up to as the "gurus" being kicked out the door.
So as the economy heats back up (albeit slowly!) I think some companies will be reconsidering the idea of employee retention. Considering individual productivity is up (has to be, chances are you are doing 2 or 3 jobs!) it becomes more expensive to lose someone. Especially if they defect to your competition and take their knowledge and skill sets with them.