When considering the optimal circumstances for engaging emergency heat, what specific indicators should be taken into account? Is it a matter of merely reacting to frigid temperatures, or is there a more nuanced approach that involves evaluating entire heating systems? For instance, should one be aware of the peculiar characteristics of the heat pump, and how it operates under varying external conditions? Additionally, could the age and efficiency of the existing heating system play a critical role in this decision-making process? Furthermore, how do differentiating factors, such as unusually low outdoor temperatures or prolonged periods of power outage, influence the necessity of activating emergency heat? Are there indications, perhaps the subtle signs from your thermostat or the performance levels of your furnace, that suggest the timely adoption of this heating mode? In what ways can understanding these variables lead to more informed choices about when and how to utilize emergency heat effectively?