Organic molecules producing thermally activated delayed fluorescence (TADF) have emerged as promising dopant materials for electroluminescence. The success of the TADF molecules originates from their ability of harvesting all the electrogenerated excitons for photon emission. Operational stability of TADF materials, however, has yet been fully investigated. We investigated the molecular factors that govern stability, using a series of systematically tailored TADF molecules based on 1,3,5-triphenyltriazine. Synthetic control in our TADF molecules involved variations of donor parts, which enabled semi-quantitative assessments of molecular parameters including a bond-dissociation energy and an exchange energy. We observed varied extents of degradation of the molecules upon photoillumination or bulk electrolysis. We believe that our studies can provide useful insights into the molecular strategies to prolonged device lifetime.