Another 13.1?

It's a tough choice. I'd like to set myself a challenge, but not one which will take over my life. I want to do something satisfyingly hard, but not crazy. I've just done a half-marathon in my best time ever and, despite still feeling exhausted, I'm keen to build on my good running form. It was suggested to me, while I sat in the car swigging water less than an hour after I finished on Sunday, that it might be an idea to train for a marathon. Well, it's certainly an idea, but is it a crazy one?
My intention this year was to run the same four races I did last year. I have completed two and entered the third, so my thoughts are turning to the winter. Last year I ran the Hog's Back, which was fun, but only 8.2 miles. A reasonable distance, but something and nothing, not a distance which can easily be compared with any other. The year before I did a 10 miler. A very hilly 10 miler. But it was a long way from home, and there is always a point at which I wonder why I am in the car longer than I am running, when I could run the same distance from my front-door and be home for breakfast. Both of these have the advantage, though, of a previous time to compare this year's with.
I've found a half marathon just over an hour away, mostly canal paths, which looks a good option. But then, there is the Greensand Marathon. Not just a marathon, but a marathon with a vertical mile of ascent and descent. Not just a marathon, but a marathon with a quarter-way cut-off point of 70 minutes, which doesn't sound too bad until you remember the vertical mile. And the fact that it's all off road. I won't be able to move for a week afterwards. At least. I won't educate my children much for a week afterwards - unless setting a role model of setting challenging goals counts as education. It's expensive, but it's close to home, and somehow, when it's an option on the table, everything else sounds just a little bit tame. So, it's an idea. But is it a crazy one?