My uncle is a 65 year old COBOL programmer who has never been out of work.
I have high hopes for Ruby on Rails -- it won't have the longevity of COBOL, but it's gonna be a nightmare of a legacy system ;-)
It's a tricky career path but if you just want to count down the clock on your career and build up cash for early retirement it does have it's benefits.
The language itself is actually pretty cool. I enjoyed working in it and learning legacy stuff; it made me appreciate what we do have now.
The work of maintenance on old systems is just annoying and boring. That's all you generally do. Few people are rolling out new things in COBOL even on older systems. It's just maintenance, debugging, and providing support for new features when the domain you are working on requires it.