There is a huge difference between marriage and cohabitating...
If Married..
1. What's mine is yours, what's yours is mine. Forget saving for now even though you could, and dump money in that student loan as if it was your own!
If Cohabitating... for less than 5 or 10 years, so far, and not currently considered "married" by law..
2. You deal with your shit, I deal with my (nonexistent) shit. Split all expenses according to our respective income % evenly. LOYL pays off loan at the rate they see fit (which will be slower and result in more interest paid) while you stash away savings for retirement, a house, etc. No to house savings by only one person for owning as a couple -- that down payment should be shared, too, unless the house is only in your name / your own personal investment.
Cohabitating -- you need to be able to cleanly split up assets if you split. Married, well, you made a vow to support and protect each other for life, and that extends to your finances if you split up, if you don't love someone enough to help them with their life for a time after a divorce, don't get married. IMO.