We performed a systematic evaluation of the diagnostic performance of LAFOV PET/CT with increasing acquisition time. The first 100 oncologic adult patients referred for 3 MBq/kg 2-[18F]fluoro-2-deoxy-D-glucose PET/CT on the Siemens Biograph Vision Quadra were included. A standard imaging protocol of 10 min was used and scans were reconstructed at 30 s, 60 s, 90 s, 180 s, 300 s, and 600 s. Paired comparisons of quantitative image noise, qualitative image quality, lesion detection, and lesion classification were performed. Image noise (n = 50, 34 women) was acceptable according to the current standard of care (coefficient-of-variance_ref < 0.15) after 90 s and improved significantly with increasing acquisition time (P_B < 0.001). The same was seen in observer rankings (P_B < 0.001). Lesion detection (n = 100, 74 women) improved significantly from 30 s to 90 s (P_B < 0.001), 90 s to 180 s (P_B = 0.001), and 90 s to 300 s (P_B = 0.002), while lesion classification improved from 90 s to 180 s (P_B < 0.001), 180 s to 300 s (P_B = 0.021), and 90 s to 300 s (P_B < 0.001). We observed improved image quality, lesion detection, and lesion classification with increasing acquisition time while maintaining a total scan time of less than 5 min, which demonstrates a potential clinical benefit. Based on these results we recommend a standard imaging acquisition protocol for LAFOV PET/CT of minimum 180 s to maximum 300 s after injection of 3 MBq/kg 2-[18F]fluoro-2-deoxy-D-glucose.