In this paper we investigate what kind of failures are likely to happen in LED based streetlighting luminaires and what are the requirements for being able to detect these by means of thermal transient testing. Based on preliminary results of long term stability studies of LEDs done in cooperation with the Pannon University in Veszprém, Hungary one should expect degradation of different thermal interfaces. Except the die attach, the relevant thermal interfaces are likely to be detectable by relatively low resolution thermal transient measurements. The measurement hardware can be realized as an add-on to the LED driver circuitry present in the luminaire. Problems related to lack of K-factor calibration are also dealt with.