My current partner likes anal, but she doesn't want it all the time, either. I won't go into it here, but she is younger than me (20s), and it seems like anal is a standard thing... maybe a generational thing (I'm not complaining!).
She likes her ass eaten, too, and wants to do the same to me. I have no problem licking her ass, and it feels good when she licks me, too, but I'm not a fan of going much further than that.
As far as frequency, sometimes it might be a few times a week, especially if she is having her period. We might go a week or two without, and then it picks back up again. I think she would do it as often as I want, but it is more fun (I think) when it just happens.
She can cum from anal, which I think helps with our frequency. I've always been amazed when watching vids of amateur guys and women where he pulls out of her pussy and just slides right into her ass. That is not how it works for us at all! I think if I just went balls deep, that would be the last time I ever got to do it, haha. She is tight all the way around, and it takes quite a bit of lube and slowly slipping a bit in, holding, pulling out a little, and going in a little bit more.
I don't know if you are asking how to work this into your sex routine, but if you are, I would just recommend approaching it just like she was going to put a dildo up your ass, haha. While I don't particularly want that, I'd want it to be slow, careful, and with plenty of lube if it happened
Forget the porn star fucking you see and pay attention to how she is responding, sounding, and the feedback she is giving you.