Is it okay to be engaged when you're 18?

My Boyfriend and I have been going out for 6 months but have known each other for a year and a half. When we go to college we will have been going out for just short of a year. We are a great match. Hes very smart and caring and a perfect catch. I know he will make a great husband and eventually a great father. Each of us is going to college ( on opposite sides of the united states). We both know we want to be together forever. We are considering getting engaged before college, being engaged in college, and getting married afterwards. We would be engaged for about four years. Since we already know we want to get married, it shouldn't matter when we become engaged. I would help as far as confidence when we're away from eachother. symbolic of our attachment. and good for other girls trying to pick him up. We would survive without the rings, but since we already know we want to be together forever it might be a good touch. We will wait until after college for the marriage. Is it okay to become engaged or do you think other people will think its too soon?