I do actually think that it is possible to love one person your whole adult life, but it is chancey. The truth is the people grow and change - sometimes not in the way we expect or want. IMHO, many of us marry someone (particularly women) whose potential we fall in love with. Men and women, equally, fall in love with people who provide them with something they can't give themselves (and no, I do not mean sex!). This is not a mature love, but a love that - it seems to me - few people outgrow.
I am not sure that it even has much to do with age; rather, it is about emotional maturity. For myself, I was really not together when I married stbx. I was unhappy with myself in many ways. I felt that he needed someone to take care of him, which I did. I was undemanding, to the point of being disrespectful to myself, and allowing him to be also. The breakdown of my M was not all my fault - not by a long shot! - but my decision to marry him in the first place was probably not a good one, in retrospect.
No one here can know what will happen with you and your H, but I do believe that you can find lasting love, either with him or with someone else. It will depend more upon your own emotional place, and that of your partner, than on any kind of rules about love (IMHO, of course).
Take care of yourself, Nicola
Life isn't about finding yourself; it's about creating yourself My thread: Trusting God's Plan