At 13, I was the nerdy, scientific type.....
One Sunday afternoon, right after lunch, my parents and siblings had gone away to visit my grandparents. Somehow I was excused from this duty. I had been having erections all morning long, so shortly after they left I went to my room.
My homework desk was the same height as the base of my cock. I took a clean sheet of white paper, and masturbated over it. My prick only slightly subsided. I jerked off again. I was still feeling the urge, so made myself come a third time. The paper lay on the desk before me covered with sperm splatters, which I proceeded to measure with a ruler. I marked them '#1', '#2', and '#3'. I measured their lengths with my ruler, noted this on the paper, and added the approximate times they occurred. In those days my refractory period was usually less than five minutes although by the third or fourth 'load' I might be out to fifteen or twenty minutes.
On several occasions in my life I have frigged over a sheet of paper, mainly out of curiosity to see what my cum was like, whether thick or thin, or as great in quantity as at the last time I had masturbated over paper.
One benefit of regular masturbation was that I no longer came involuntarily in the night, messing my pyjamas. I kept a large box of tissues at hand, and upon feeling my nutsack tighten whilst stroking, I would quickly grab three or four tissues and cover the head of my cock, catching my cum before it fell on the bedsheets. I would learn later that my mother appreciated this as she didn't have to clean up a messy bed each morning.