I don't think age has anything to do with agreeing to marrying someone. I even think that you should be so careful before moving in with someone. Get to know your person really, really well. See how they react with your friends, with your family and parents, in difficult situations, and when they are so very, very tired. If you life what you see then you have a good one.
If you move in an out quickly with people it must be to terribly hard on yourself. Be like getting a divorce over and over. We have so many depressed and melancholy people around because they got too involved too quickly and had to put up with awful situations. Sometimes it takes months to find out that someone has mental healthy problems and would be very difficult to have a life-long relationship with them.
So write up the list of what you are looking for in a partner. Nothing superficial. Things life respect, energy, initiative, ability to think outside the square etc. Nobody is perfect, but choose carefully.