The on-detector readout installed in the CMS Electromagnetic Calorimeter (ECAL) has been tested to resist the radiation environment expected for ten years of LHC operation. The Phase II upgrade programme of CMS foresees additional LHC operation at higher luminosities until about 2035. Qualification of the on-detector readout for this longer running time, for the existing electronics and for those elements that will be replaced prior to Phase II, is required. Accelerated ageing tests of the present electronics have been performed to achieve a total estimated lifetime of 40 years. These new results will be summarized in this presentation.