Good question. I’d say whatever you two want to call each other.
I am married so that’s no brainer how to call my husband but I had a long term significant other for 8-9 years and at least last 5 of those we lived together. We referred to each other as boyfriend/girlfriend. We were up in age too.
I never thought of calling him my husband but I had family members who referred to him as such. Like “where is your husband?” It never sounded right to me.
And one time I had this funny story. My niece 5-6 at the time asked me why I had two husbands. I about to fell over. I in fact had zero husbands at the time. She was referring to my daughters father, who is my ex husband, and my live-in boyfriend/significant other , whom she heard some people called my “husband”. So poor kid thought her auntie is bigamist or something.lol I had hard time explaining to her.
I am not a traditional person but I don’t call someone I am not married to as a husband. Like if I indicated everywhere that I wasn’t legally married why would I say I have a husband BUT I don’t care either way what others call each other.
Don’t give it another thought. If you two are commited to each other, then that’s what matters