The commercialization of self-emissive quantum dot light-emitting diode (QLED) faces several critical challenges. A primary obstacle is the reliance on acid-induced positive aging protocols using UV-curable resin to enhance device efficiency and brightness. However, this in-situ aging process is difficult to control, which undermines device fabrication reliability such as causing non-uniform luminance, accelerating degradation and introducing batch-to-batch variations, thereby impeding industrial scalability. Herein, we propose a solution-processed thermal treatment strategy to modify ZnMgO as electron transport layers in QLEDs. Characterization reveals that thermal treatment of ZnMgO leads to a 25% decrease in oxygen vacancies, which reduces the requirement for the positive aging process. Furthermore, the approximately 30% increase in nanoparticle size of thermally treated ZnMgO improves structural stability. Consequently, the resulting QLEDs exhibit enhanced electroluminescence uniformity, achieve a high luminance exceeding 60,000 cd/m² at 3 V, and triple their operational lifetime (T₉₅@1000 cd/m²) to approximately 20,000 h. The proposed thermal engineering protocol for ZnMgO provides a viable route toward reliable industrial-scale production of high-performance QLED displays.