My wife and I are in our 30s and married almost 10 years. Our sex life has had many ebbs and flows over the years. We've had anal sex exactly twice, both times before we got married. I'm into pretty much anything kinky, and the wife is certainly a sub (being spanked makes her very wet, the harder the better) but only when she's in the mood, and that comes in phases. It's easy for us to get in ruts where sex consists of nothing but quickies.
Long, long ago she shared fantasies with me about having anal sex. As I said, we did it twice when we were much younger. But that was back when she liked to smoke pot with me. The thing about my wife is that she is a very anxious person, and she carries a lot of that in her muscles. I think nobody gives Freud's theories any credit any more but she does seem to be a classic anal-retentive type. Anyway I think the pot helped her relax when we successfully had anal way back when, but that's beside the point. Nobody is smoking pot anymore.
Anyway, after many many years of no anal play at all, recently things have picked up again. When we were doing some other bdsm type play (I had her tied up), she was playing with her vibrator after I came and she asked me to talk dirty to her. She asked me to tell her what I wanted to do with her, any fantasy I had, and I told her I wanted to be able to fuck her in the ass. And more than that, I told her that I wanted to train her ass so I'd be able to fuck her in the ass easily all the time. Well, this got her turned on quite a bit. She ended up having a very intense orgasm using her vibrator after I slid my finger in her ass, and that was after she had said out loud that she wanted me to train her to be my anal slut. And this is from an extremely shy woman who hardly ever opens her mouth in the bedroom.
Well, that was a few months ago and we've done some anal play since then, but we are still far away from having anal sex again. I've used a very small butt plug on her during foreplay, and a few times during sex. She has graduated to a slightly larger one but it's still very small and much much smaller than my thick cock. Once I was able to convince her to use her plug on her own time to get her asshole used to being stuffed, and she did wear it for 20 minutes while she was at her desk, but in general she doesn't not respond well to those kinds of suggestions. She can be submissive, but it only works if she initiates her submission, if that makes any sense.
And the latest is, last week she did invite me to use her body however I wanted, and unfortunately I was a little too ambitious. We have a 3rd plug that is a bit bigger than the one she has been using (still much smaller than my cock), and a bit harder (as opposed to the others which are just a little squishy), and she was responding so well to my finger in her ass I thought I would give it a go. I had her lubed up quite a bit and I tried to take my time to slide it in slowly, and it got nearly all the way in...and when she had moved up to the bigger plug the first time something similar had happened where I did have to give it a bit of a push to get it in, and she yelped, but once it was in she enjoyed it. However this time I pushed too hard and it was too painful for her. She cried a bit and we stopped with the anal play, although remarkably it didn't completely derail the sex session.
She has been a bit leery of going back to anal since then, but I am sure she will be ready to get back on the horse soon. I've just touched her ass a bit and pressed on it with my finger the last 2 times we had sex and she has been ok with it.
I'm not sure how to get her to the point where we can actually have anal sex though. I'm afraid that the frequency of anal play with the plugs is too low (once a week at *best*) and that it would have to be more often for her to really get ready for something bigger. Although, I'm sure I just need to be patient.
Assuming we do have anal sex, the idea of going anal only excites me greatly. I honestly don't think she would ever go for that, but wow it does sound amazing.
Anyway, if you read that much thanks for sticking it out

-Kink