Patrick, I have similar situation to yours. Only my wife is the taller one. Also, I am far more interested than she is in improving and continuing to dance at the studio or in studio shows, which we have done several times. I'm not interested in competing too much, as I did that when I was 30 years younger, but not for very long. Because my wife is not as interested, I often find myself dancing with other ladies at social events or even the lessons. My wife doesn't seem to mind. She has, in fact, encouraged me to dance with ladies at events who don't have partners and maybe traveled a long way to attend the event. All of that being said, I would prefer that my wife was a dance partner who had the same enjoyment and desire to improve, but it's just not a priority for her, at least partly because she is an aerobics instructor and her feet and knees take enough pounding. As long as she doesn't mind me dancing with other women (or if I had a different partner for a show or program), then I guess it's OK.
Not to get nosy, but does your wife have no interest in dancing at all? Or doesn't have the time to practice, etc.? (That is part of our problem ... my wife and I are on different schedules much of the week). The best way to describe it for me, is that it's always been one of many sports I enjoy, and it is also a main hobby.
