All of my horses are "over the hill". My youngest is Scout, who is thirteen. Annie is fifteen and Nadia is a whopping twenty five! Nadia is showing a little stiffness, but otherwise she's fine. She really perks up under saddle. She loves trail riding and is very willing to gallup and even prance. I don't ride them all as often as I'd like, mainly because of my work and school schedules, but they are all in good health and have always been sound. They live in covered stalls with large runs and I turn them out for exercise almost daily. They are fed a diet consisting mainly of hay, horse cookies and various treats, a little grain, free choice mineral block and fresh grass whenever possible. They also get wormed, shots, hoof care, fresh water, exercise and lots of love.
I think Arabians finally settle down in their early teens. Before that, they're goofy, at least Annie was. And I've had others. Barry was a five year old gelding that everyone thought was a stud colt. Shahreen was seventeen when I sold her and Leigh took her competive trail riding well into her twenties (the horse, I mean).
Consider Elmer Bandit. He's a 37-year-old Half-Arabian gelding that completed the Indian Territory North American Trail Ride Conference (NATRC) ride over Memorial Day weekend, finishing in sixth place and bringing his lifetime mileage total to 20,360. Kudus to him and his rider. And he doesn't even hold the record for mileage. An American Saddlebred, Wing Tempo, has that honor.
Then there is the story of an old throw away Arabian that was recovered and used by a queen, rodeo queen that is. See here: http://winfieldcourier.com/main.asp?SectionID=1&SubSectionID=1&ArticleID=24923&TM=16736.66
People ask me how long do horses live? I tell them the average life span is twenty-five. This is because many horses die sudden and unexpected deaths early in life (I lost a seven year old, tragically). But they can easily live well into their thirties. At least, I'm hoping so.