I have 20 pieces of UAV image, and using ArcMap i want to mosaic it all to become one raster but step by step, 

what i mean is mosaic image 1 & 2, image 3 & 4 ...... then result of 1&2 mosaic with result of 3&4......, then mosaic them all (i do this to prevent crashing so my time didnt wasted).

Should i build statistic and pyramid after every mosaic step, or i can just skip build pyramid and stat for every mosaic i build, and just build mosaic on the last step (when mosaic all of it)?