Marketing has studied the permanence of a client within an enterprise because it is a key element in the study of the value (economic) of the client (CLV). The research that they have developed is based in deterministic or random models, which allowed estimating the permanence of the client, and the CLV. However, when it is not possible to apply these schemes for not having the panel data that this model requires, the period of time of a client with the enterprise is uncertain data. We consider that the value of the current work is to have an alternative way to estimate the period of time with subjective information proper of the theory of uncertainty. To achieve the above we propose, through a numerical example, a methodology that uses in its first phase the Fuzzy-Delphi method, with a group of experts, to accomplish an estimation of the lifetime period of the client within an enterprise, expressed as a trapezoidal fuzzy number, and to get a better consensus of the previous result, as a second phase, we submit such information to another group, different from the previous ones, obtaining a reduction of the size of the interval defined by the initial trapezoidal fuzzy number.