"So far this experiment with starting a 7 year old says it's a good thing.
Angie"
I have started four horses after the age of seven and have found no problems. A few years back, I bought some unbroke broodmares that were nine years old and had them broke to ride. All of them came around nicely, made very good trail horses, and one turned out to be a great 100 mile endurance horse. In fact, my experience with these mares convinced me that starting horses under saddle a little bit older is actually a good practice, especially with endurance horses. It changed my entire point of view of what "old" is in terms of performance expectations.
I know from an equine "industry" point of view that this attitude is really not feasible. Luckily, I really don't have to follow industry standards. But, until my experience with these 9 year old mares, I didn't realize how much this industry standard influenced my thinking when looking at endurance prospects. I look back now and wonder how many good horses I passed on because I thought they were too old to start and because of their age would not be worth putting time into because they would be "too old" by the time they were conditioned up.