even the ages you stated are exactly the same in my case. If you ever find the answer to this, please share it with me, because I have been struggling with this for some time now.
What I have figured out about this is that our H's were so young when they got involved in a serious r with us. So, when most guys their age were dating around and "having fun" in their twenties, our H's were in serious, committed Rs. Now, that's not to say they didn't have fun with us, but I think they found themselves in their thirties realizing that they missed out on something.
I know in my H's case, he even said this. One of the things taht drew him to the A was that he never got to date as an adult. Now, neither did I and I'm not about to have an A, but I'm just trying to offer some explanaion of what's goign on. I think that when another woman comes into the picture, they don't have the will or strength to say now. It's just too tempting.