I have a hard time believeing that even though you have a great relationship, asking yourself if it will last or hoping this does not ever cross one's mind. ESEPCIALLY when it comes to the "For Worse" part of the commitment. I concur totally with Savannah that it is completely natural to wonder, but do not obsess over it, as I also think that you are what you become so if you dwell on something long enough, somehow you make it a reality. If you have the commitment to each other than it is half the battle, love hangs on and ties a knot when you reach the end sometimes.
As far as the money situation, we use a simple solution. We have 4 accounts- joint checking to pay the bills, a joint savings and 2 separate accounts (individual accounts). As long as home is taken care of neither of us can grip about the money situation and be concerned about fighting over money. Home first and then you are free to do whatever you like with your individual. Sounds crazy perhaps but works for us.