This question is very subjective and is of no technical detail, however since MSE is a place for working mathematicians, I thought I'd ask here to get the best answers!
As a prospective graduate student in mathematics, I have come to know the mountain of knowledge is quite tall and there is much to learn, even past graduate school.
However, I would like to think that if my goals of becoming a professor come true and I become a specialist in an area of math, that even though I specialize in one area, that I would still love to continue learning other areas of math.
As a working mathematician in a certain area, do you ever find yourself as a working analyst picking up Hartshorne and finishing it 3 months? Do you as a differential geometer find yourself interested in Diophantine equations and pick up a graduate number theory book and go through the exercises?
If this is the case, do you normally read textbooks as a fulltime professor and go through exercises just as in university?
Or, is it unrealistic to spend time on new material when this time could be spent on your area of research?