SUBREDDIT: r/relationships
TITLE: My [20 M] girlfriend [19 F] of 2 years, has no idea what she wants to do in life (career wise), how important is knowing your goals for a relationship to last?
POST: I realize we are still young and we are both in college, but she has no idea what type of career she wants, and doesn't like the sound of any that get suggested based off her majors (she has changed majors a few times). 

It bothers me since I'm kinda close to graduating and know exactly what kind of job I want, what I want my life to be like, and things like that. Where it seems like she just thinks a job will show up when she graduates and everything will be good. And I don't think I would have a good enough job to support both of us and even think about having kids (we both know we would want kids WAY in the future)

I'm wondering from the view point of older people how important is it for a SO to know what they want in the long run?
TL;DR: 
How important is it for a couple to know what they individually want in life and to see if their goals are compatible?