I don't think there is anything wrong with living together as long as the end goal of both partners is to get married in a year or two down the line. I think it's actually important to live together before marriage to familiarise yourself more with the other person, it's possible that even though two partners are compatible, their living habits are a dealbreaker. But yes, the end date needs to be established.
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~