I like Shirley very much, but I do agree with you about the age factor. We had a Latin teacher at high school, then in her early 30s we thought, whose name was Shirley, and ten years later when I was teaching, I had a pupil surprisingly named Shirley. But they were the last that I've encountered.
Thinking about that, it occurs to me that I also like Sheila, and it also seems to be pretty well extinct.
Shirley Margaret
Shirley Rosanne
Shirley Melissa
Shirley Alison
Shirley Theresa