The March 2010 update added an additional condition to the spirit companion's duration such that it expired if call spirit companion was used again. That change prevented multiple spirit companions from being summoned. The October 2010 update then reverted that change, and replaced it with a requirement that the spirit companion cannot already be present. That change still prevented multiple spirit companions from being summoned, and also prevented shamans from dismissing and resummoning the spirit companion in one minor action.