A method of estimating an elapsed lifetime (L E) of an LED based illumination module, the method being performed by a processor of the LED based illumination module, the method comprising the steps of: • measuring an accumulated elapsed time of operation of the LED based illumination module; • dividing the accumulated elapsed time of operation into a plurality of time segments (i), each of a predetermined duration (• T); • for each time segment (i), calculating a representative value of an actual operating condition (T Ai, I Ai, RH Ai); • calculating a plurality of incremental acceleration factors (AF i), each incremental acceleration factor being calculated for a respective time segment (i), • wherein the LED based illumination module has an expected operational lifetime when operating at a nominal value of the operating condition (T N, I N, RH N), and • wherein each incremental acceleration factor (AF i) is calculated as a function of the respective representative value of the actual operating condition (T Ai, I Ai, RH Ai) being below or above the nominal value of the operating condition (T N, I N, RH N), such as to extend or reduce the expected operational lifetime of the LED based illumination module for the respective time segment (i); • determining, over the plurality of time segments (i) of the accumulated elapsed time of operation, a cumulative acceleration factor (CAF overall) based on the plurality of incremental acceleration factors (AF i); and • estimating the elapsed lifetime (L E) of the LED based illumination module by scaling the accumulated elapsed time of operation of the LED based illumination module with the cumulative acceleration factor (CAF overall). • measuring an accumulated elapsed time of operation of the LED based illumination module; • dividing the accumulated elapsed time of operation into a plurality of time segments (i), each of a predetermined duration (• T); • for each time segment (i), calculating a representative value of an actual operating condition (T Ai, I Ai, RH Ai); • calculating a plurality of incremental acceleration factors (AF i), each incremental acceleration factor being calculated for a respective time segment (i), • wherein the LED based illumination module has an expected operational lifetime when operating at a nominal value of the operating condition (T N, I N, RH N), and • wherein each incremental acceleration factor (AF i) is calculated as a function of the respective representative value of the actual operating condition (T Ai, I Ai, RH Ai) being below or above the nominal value of the operating condition (T N, I N, RH N), such as to extend or reduce the expected operational lifetime of the LED based illumination module for the respective time segment (i); • wherein the LED based illumination module has an expected operational lifetime when operating at a nominal value of the operating condition (T N, I N, RH N), and • wherein each incremental acceleration factor (AF i) is calculated as a function of the respective representative value of the actual operating condition (T Ai, I Ai, RH Ai) being below or above the nominal value of the operating condition (T N, I N, RH N), such as to extend or reduce the expected operational lifetime of the LED based illumination module for the respective time segment (i); • determining, over the plurality of time segments (i) of the accumulated elapsed time of operation, a cumulative acceleration factor (CAF overall) based on the plurality of incremental acceleration factors (AF i); and • estimating the elapsed lifetime (L E) of the LED based illumination module by scaling the accumulated elapsed time of operation of the LED based illumination module with the cumulative acceleration factor (CAF overall).