Want to get married!

I've been with my SO for going on 3 years. We've talked about marriage, but he still wants to wait a few more years until we are more stable in our careers (around 2)...I would even settle for an engagement now, a long engagement period, and getting married later just as an outward expression of the commitment. Has anyone been in a similar situation? How did you "nudge" your SO in that direction?