It's definitely too much if it interferes with your sexual relations with your girl. Other than that, I think the lines get a little fuzzy....
I went with a guy when I was maybe 18 who jacked off at least a couple times a day, and had since he was 17...he was like 25 at the time that I knew him. We had sex constantly. He just had a hard on all the damn time and was extremely sexual, all the time. Had he not been so personable and a real sweetie, I would never have gone near him, but it somehow seemed acceptable for him, but definitely not normal by any means. I think he needed psychotherapy.
I dated another guy who did it almost every morning in the shower. That struck me as normal.
My husband almost never does it, and with our conflicting schedules, sometimes we're lucky if we can squeeze in sex any more than once or twice a week...then he gets "blue balls" and cries about it. THAT seems unhealthy, I wish he would do it more.