A system and method for estimating the longevity of an implantable medical device (IMD). In one embodiment of a method for estimating a life of a power source of an implantable medical device, a first life estimate of the power source is determined based on a first open-loop value corresponding to an open-loop parameter for open-loop therapy delivery, a first closed loop value corresponding to a closed-loop parameter for closed-loop therapy delivery, and prior usage data corresponding to prior therapy delivery. The first life estimate of the power source is displayed. The first life estimate displayed includes a first open-loop portion associated with open-loop therapy delivery and a first closed-loop portion associated with closed-loop therapy delivery.