To answer your question, no, it hasn't been AO our entire 30 years together. I would say it's been more like for the last 22-24 years. After the birth of our son, my wife didn't want to get back on birth control, so we started having more anal sex during that period of our lives. We just sort of gravitated in that direction with no real conscious decision to be living any certain lifestyle. In fact, I had never heard of an AO lifestyle until I found this site. I have desired for the longest time to find other couples like us, but up until now hadn't found anything substantive.
Anal sex wasn't always smooth sailing for us. There were hurdles that both of us had to overcome before we were able to fully enjoy anal sex without the stigma that often accompanies it; perhaps a discussion better left for another day.
Given you both have such an obvious preference for anal I have to ask - why still continue with the vaginal at all? Occasional desire for variety? I know some couples choose to still have vaginal once in a while just because they feel "they should", almost ritualistic or out of habit.
You've given me something to ponder, as I haven't really given much thought as to why we continue having vaginal sex, given our preference for anal. I guess you're right, though. It's probably just a diversion. As I was thinking about your question, it dawned on me that even though we still have vaginal sex on occasion, even then we still usually finish with anal. It is very rare that we ever just have vaginal sex, start to finish.
You carry on doing just as you have been. Anal/vaginal isn't some kind of binary choice. I find you can mix as you please, and different relationships have gone different ways.
I do understand those on either side, and that there are those who like to keep to one activity exclusively because they like one act that much. Every human being is an individual.