All effects are constant on self:
After defeating Karstaag the Frost Giant, the Nerevarine encounters Hircine once again. He states that the Nerevarine has "earned the greatest honor that can be bestowed upon a mortal" by becoming his prey. He proceeds to ask the Nerevarine which attribute makes a hunter great: strength, guile, or speed. If the Nerevarine responds with speed, Hircine transforms to Hircine's Aspect of Speed. When he is defeated in this form, this amulet can be obtained from his remains.