It may seem obvious, but it’s amazing how often this simple tenet is overlooked. If you’re training a staying horse to run distance races, fast work should tend to focus on longer gallops. The fast work of a sprinter should be shorter, faster works.
The problem with this approach is that you literally get what you train for. By concentrating too much on longer, slower gallops, you tend to end up with a slow horse. Too much focus on half mile breezes will result in a horse that goes fast for a while, but that may not be able to finish off it’s races.
The answer is a combination of the two. Author Tom Ivers used to talk about a “tapered series” of gallops, whereby, targeting a 1200m race, you might first work over a mile, then three days later work a good strong 1200m, then three days after that work a “fluffy” 5/8 – not too hard – then go racing. With this sort of work, you develop the ability of the horse to stay, without compromising too much on speed.
I can’t recommend Tom Ivers’ books strongly enough – particularly The Fit Racehorse II (see my review here), and The Complete Guide To Claiming Thoroughbreds. The Complete Guide focuses on claiming races in America, but the training principles can be applied anywhere.