An analysis of the content and features of works on the extension of the assigned service life is presented, a method for determining the average value of the residual resource is developed, and the necessary number of technical products and the duration of observations for the extension of the resource are estimated. The experience of the Joint Forces operation in the east of the country has revealed significant shortcomings in the reliability of armaments and military equipment during operation, which are primarily due to the fact that the condition of a significant number of samples of weapons in operation is close to the limit. Therefore, it is considered appropriate, based on the analysis of the content and features of work to extend the service life (resource) of samples of weapons and military equipment, to develop a methodology for determining the average value of residual resources and assess the required number of samples of weapons and duration of observations. For most models of armaments and military equipment involved in a joint force operation, this problem can be partially addressed by adjusting (extending) the assigned service life (resource). The accumulated experience of development and operation of armaments and military equipment shows that in some cases the duration of operation of armaments may exceed the normative terms specified in the technical documentation. Therefore, it is very important to have methods for calculating their residual resource for statistically significant support of the decision-making process in the implementation of their development plans. To achieve the result, work on extending the assigned service life (resource) of weapons samples is analyzed on the basis of data on their operation or using methods of accelerated consumption of resources and service life and determine the average value of their residual life based on operational tests. To solve this problem, an analysis of the content and features of work to extend the service life (resource), developed a method and content for determining the average value of the residual resource and estimated the required number of samples of weapons and the duration of their observations when extending the resource. The analysis of works on extension of the appointed service life (resource) of samples of armament and military equipment testifies to expediency of use of this tool of improvement of their reliability at operation. Further research should focus on the economic assessment of the size of the resource that is being extended, as solving the problem of improving the reliability of the operation of weapons models by extending the resource is associated with certain economic costs. And this, in the end, saves the much-needed resources. Keywords: technicalproduct, operation, servicelife, lifeextension.