Im playing with barrels and poles on a 18 year old Arabian. She wont be a buckle winner but she has fun and I have fun. She's also getting into shape to do some endurance riding. We wont be doing 100 mile rides (as my legs may fall off lol) but we do 12 mile trail rides almost every weekend and its in the mountains (12 miles round trip and we do it in 45 min to an hour and 20 min). So no 8 is NOT too old. Its a good age. They are done with being babies and are done growing. But don't get a green horse. My arab has some gaps and it shows. For a first horse get one that at lest understands what your cues are, then you can train it for barrels and such.