Happy birthday, in case I forget.
I'm a little older than you (birthday is on the 30th), and I have been pushing myself. I do half marathons (13.1 miles) pretty regularly now, about once a month. I hope to do that until I drop dead!
While I would almost like the idea of doing a full marathon or even more, I just don't think I'm interested in spending more than about 2.5 hours of my day running, which is about how long 13.1 miles takes me. Otherwise I might do those. I just have other interests as well as running.
My wife thinks the running I do is crazy though. That's why I mentioned it.