Hi Cheersdarling,
Thanks for posting your question. I'm not a doctor, not any kind of medical authority, but I do have herpes and have done some research on this.
From information I have seen, it appears that what you say is correct. Once you have antibodies of HSV 1 in your system, it is difficult to get HSV 1 again on another part of the body. It is still definitely possible, but it's not common. You should still be safe and not have sex while either of you is having an outbreak. The advantage of you both having it is you can talk about it and be aware of each other.
For more information I suggest you take a look at the Genital Herpes Prevention, Causes and Risk Factors, and Coping with Herpes pages.
PJ