I'm 18 and my fiance is 26. Marriage tips?

i knew him since i was 15 and he was 23 and we spoke long distance for a while til he moved back here when i was about 17 and we dated. i'm so in love with him and i'm dying to be his wife and he wants to be my husband. we invisioned our lives together and we are planning. i know i'm young and he's kinda young too but me and him aren't into the partying youthful lifestyle me and him had to grow up quick yet my family thinks i am too young and rushing things i should set up my career and have fun but i am going to college he's even helping me pay for it but that is still not enough anyway him and i are engaged i want to get married soon. He and i already bought a house he is just putting some final touches to it. he is somewhat of an heir and has money and is always spoiling me with shopping sprees and vacations and cars but I just want him. He's a great guy, simple man, home body and responsible and doesnt have much living family so i'm thinking after the wedding i want to try to get pregnant after a year ..... Is this too soon? he wants kids too about 4. Anyway what can i do in our marriage to keep it long lasting? Will things change after we are finally husband and wife? Tips? i'd love to hear from someone who married young &/ or married someone within a 8-10 age gap?