A couple more things…
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Try out your rain gear ahead of time. Really ride in it, for several hours. It's no fun riding for hours when soaked through to the skin.
Get a quarter sheet for your horse in case you are riding in wet, cold weather. I bought a "Bun Warmer" that ties to the back of my saddle and can be rolled up when not in use. It's very helpful to prevent cramping. It's water proof.
Even though your horse has always been calm in group rides, the atmosphere at the start of an endurance ride is amped up. There will be many horses travelling along at speed. When your horse is fresh and he realizes what is up, he's likely to be stronger than he's ever been. Consider tactics to cope with this.
The long-slow-distance work mentioned above will give you an idea of good pacing for your horse. I've seen people allow their horses to wear themselves out at the beginning of a ride "to take the edge off". Just because they feel like running doesn't mean they are actually up to it for the distance. Adrenaline takes over, and your horse may overwork himself early on. You've got to know your horse and get an idea for what it takes to do some serious mileage.
Consider having your farrier apply pads under the shoes for a ride on rocky terrain.[/LIST]This is all coming from a person who has only done up to 30-mile rides, so take it for what it is worth. I've ridden a number of different breeds over the years, and I can say that they are all different. Some horses have a bravado that can be misleading, so you really have to take the time to get to know your horse during the miles and hours it takes to complete a ride. Horses who are inadequately prepared or inappropriately ridden for a competition can end up colicking or tying up.
It’s good that you are doing your homework beforehand. You are more likely to have a great ride and a healthy horse because of it.
Oh, and plan your shoeing schedule around the ride. I’d think you wouldn’t want to shoe them more than two weeks before the ride. Longer than that and he’ll have long toes that will take more work to move along the trail. Overly long toes take a toll on their legs. I don’t shoe, but I like to allow two weeks between the most recent trim and a competetive ride. Others may have different opinions. I worry about bowed tendons when I see horses with long toes at these rides, not to mention the tendency to land toe first and stumble when fatigued. Yikes.
