The increasing adoption of solar and wind power for electricity production has spurred new projects for the development of cost-competitive energy storage technologies. Among the various promising options, Li-O2 batteries deserve special attention because of their potential high specific energy, which might lead to decreased manufacturing and installation costs. Regarding the manufacturing costs, one of the steps with the most impact on manufacturing time is the wetting process, which might take days to complete. Improving this process has been crucial to reduce manufacturing costs and increase battery performance for lithium-ion batteries. This work provides an assessment of the impact of time of the wetting process on the performance of Li-O2 batteries. Li-O2 batteries were assembled using an O2 electrode based on carbon paper. The separator membrane and the O2 electrode were immersed in the electrolyte solution for 1 h, 3 h, 9 h, 27 h, and 81 h, and deep discharge trials were performed for each case. The capacity of the battery was measured and compared to the standard assembly procedure, in which the battery is assembled with electrolyte and left to rest for 72 h. After discharge, the electrodes were analyzed via scanning electron microscopy to identify the impact of electrolyte filling of the O2 electrode on the distribution of the discharge product over its surface. The results demonstrate the importance of investigating this process step in the manufacturing of batteries to ensure better performance of Li-O2 batteries.