I've been wondering this one for a while now. At what age does a horse become 'old' to you?
I was surprised to learn that horses are regularly started between two and three years old in the US. In the UK, I know breaking-in is usually done around four years old with only light work until they're five or so. So in my head, three and four year olds are still very young. I'd consider a horse to be in his prime at around eight or nine, but that a horse wouldn't reach 'middle age' until at least sixteen or so! Perhaps it's the horses I've been exposed to - e.g. Many of the lesson horses I ride are well into their twenties. I wouldn't consider a horse old until they're in their mid-twenties or later ...
I do know that when competing there are different requirements, but I do kind of get the impression that anything over eight or so is considered to be an old horse by many people! That just baffles me; surely that would be when the horse is maturing into its best performance?
So what would you consider an old horse to be?