A method of optimizing an initial performance envelope of a rotorcraft turbine engine, the initial envelope being associated with a maximum number of flying hours that the turbine engine can perform before being overhauled, and also with at least a first initial rating defined by two first initial performance levels relating respectively to a first power and to a first utilization time of the first power. The method is remarkable in that in order to perform the optimization, an alternative performance envelope is defined by modifying the initial envelope, the modification being compensated by reducing at least one of the first initial performance levels of the first initial rating. In addition, the overall service life of the turbine engine is not modified insofar as the alternative envelope is associated with the maximum number of flying hours authorized for operating the turbine engine in compliance with the initial envelope.