Whichever Horizon (or other) model you purchase, make sure you get down to the store near you and test it out yourself. Just taking other people at their word is never good enough, as you want to be sure it matches your build and workout habits.
Some treadmills simply aren't big enough to accommodate certain riders, and with others, it feels like you need an Ivy League just to figure out the control panel, so just getting a feel for the model before purchasing is vital.
Of course, if you own a Horizon Treadmill, you still will want to do some things to make sure it stays in top shape. Regardless of how quality a particular treadmill model might be, without taking some of these steps, it will not last you as long as it could. When you keep it up, this will prevent you from having to make any repairs on it for a long period of time, and therefore save you even more money down the road.