I've seen a lot of variations on this question, but this is the particular flavor that I'm interested in.

I've been in mono relationships where I try to keep it fresh with one person. I've been in poly relationships where we have multiple partners that create more variety and bring in different skills and possibilities. There are certainly ebbs and flows, but I think that my SO and I have a higher than average sex frequency, and certainly our ratio of her orgasms to my orgasms is more than usually even.

We're going on our third year of sexual intimacy. The frequency and intensity has certainly decreased since the first year, but it's also much deeper and more satisfying now. We've both gone from people who have a difficult time getting to orgasm to a situation where I've actually helped her cum while driving and she's helped me cum with a condom. Stuff we've never done before.

I'm curious about others out there. Are there women in relationships where they continue to have interesting and frequent sex even years into the relationship? What do you do to keep it going? What helps when the ebbs occur? Do you think it's sustainable?

Edit: Interesting. Some people with good experiences, but only 1 over 5 years. I wonder if that's indicative, or if this post isn't high enough up on the list to get more sample.