Arabs are excellent endurance rides. Not all arabians have the same personallity. Some are hot, while others are very laid back. Arabians have a bad reputation for being hot, but each horse has a different personallity, you just have to go out and look at the horse. You might try a morgan/arab cross. I had one and he had the best attitude in the world and could go forever. Good luck!
I wouldn't discount arabs...but if you want to look at other breeds, you might try morgans or mustangs. Apparently, akhal-tekes are good, but I don't know much about them. Or go half and half and look at morabs.
If you want a smooth ride w/ lots of endurance look ingto peruvian paso's however they are spirited. And require diffrent tack, and sometimes hard to find and when you do they will be probably be pricey. It just depends on what you want :)
You can't beat an arab as a top endurance horse. However, my father in law has a Missouri Fox Trotter that he is now doing 100's on. But all of his other horses are arabs. You could sit to that horse all day and not get sore too, so that's a bonus.
If your looking for a good indurance Arabs are the best, even though they are a bit hot they will go for ages, anyway if they are to hot you can feed them green tea leaves or calming food, which works for my horses