This paper shows a study of the variations of the supraharmonic distortion emitted by an LED lamp during and after its thermal stabilization. The study is aimed to contribute to map the uncertainties existing when quantifying supraharmonics. Measurements of the current drawn by five lamps of the same type and manufacturer are performed. Then, analysis in the frequency domain is performed and the Total Supraharmonic Current (TSHC) index is used to quantify the supraharmonic emission of the lamps. The TSHC is calculated over bands of different widths, whose outcomes are then compared to decide which bandwidth results in a less time-varying-TSHC index. It is demonstrated that the supraharmonic distortion emitted by the lamp under study experiences both an increase in magnitude and a shift in frequency during the thermal stabilization of the lamp. It is also shown how the frequency grouping impacts the quantification. It is concluded that the best choice of a grouping bandwidth is one wide enough so that it includes the whole emission band of interest. This result is a step forward to set up references for the analysis and quantification of broadband supraharmonic emission.