The invention relates to a method and device for recording serviceable lives, especially up to the technical failure, of a product and for determining the remaining serviceable life of the product. The aim of the invention is to be able to estimate, in a manner that is as precise as possible and without support provided by a model, the lifetime for any product, which is equipped with an operational data memory or has access to such a memory, without storing temporal signal progressions. To this end, the invention provides that the determination of the remaining serviceable life of the product, the recording of serviceable lives of products, and the determination of the serviceable life threshold values are carried out on the basis of operational quantities that are subdivided in classes (so-called classified operational quantities). For this, weighting factors (a_ij) are firstly determined. Afterwards, the weighting factors (a_ij) are used in order to determine weighted cumulated serviceable lives and serviceable life threshold values. This enables the monitoring of the reliability of s = 1...S products used in series.