The disclosure is directed to systems and methods by which the lifetime, e.g., remaining life or amount of life used, of variable use items, such as rechargeable batteries, battery relays, vehicles and power tools, can be determined that takes into account the conditions of the use of the item. The systems and methods involve an algorithm that can be described as accumulating points based on the real time utilization of the item, e.g., rechargeable battery, battery relay, vehicle, or power tool, and when an agreed-upon number of points have been accumulated, the item can be considered to be at end of life or end of warranty.