Use for only an hour at a time
Aheasoun prong collar is a training device and not designed for longterm use. It is not your dog's primary collar and should not be used on casual walks or outings.
Use the collar for no more than one hour and only during designated training sessions. Using the collar any longer could irritate your dog's neck.
It is dangerous to use a prong collar as your primary walking collar. Dogs learn by association. If, in the long term, your dog learns to associate pain with pulling he'll also learn to associate negativity with events that cause him to pull. Most friendly dogs pull in response to seeing other people and animals.
If a prong collar is used on every walk, your dog will learn to associate people and animals with pain. With time, he'll become timid and even aggressive in the presence of others and might even begin growling and biting.