And yet, if you didn't mind that kind of work, you could have been making a fortune from 1999 to now. You'll be retired before COBOL is no longer used.
There is a large market for maintaining legacy COBOL, SNOBOL, and various esoteric assembly codebases. Additionally APL and its derivatives are not entirely dead.
SNOBOL should be looked at, if for nothing else, for its string handling (add a brief look at Icon right afterwards). I would have killed to take APL in college, but despite having to program on an IBM 370 mainframe, no classes were offered. I'm still a little ticked.
I have over the years played with it, but I was rather annoyed that having to put up with all the disadvantages of using an IBM 370 that we didn't get some advantages.