Milso advice ?

My bf came home for the holidays and we finally made things offical , he just went back to finish basic training on the 2nd , I haven't gotten my first letter yet, I've been writing him every day since he left, I miss him so much. I know it's a bit early to be expecting a letter but I'm just so anxious. I've heard it could take weeks to receive letters, but hoping thats not the case ... how long did it take any of you milso to get your first letter?