Marriage can happen at any time after you have reached the legal age to do so. As was said above me,
there are many many things to consider, do you love the person and see yourself getting old and dieing with that person without fear or hestitation, can the two of you communicate well, tell each other everything, can you compromise and be willing to give up somethings and change other things, is there absolute trust in the relationship. Don't forget about the little things that will drive a person crazy, squezzing the tothpast from the middle, leaving a dirty dish in the sink, not being able to hang a picture on the wall and may many more. Most of all don't let other people make the descion for you, only you can do that. If getting married feels right then do.

just my 2.5 cents worth