One summer my dad took a job and studio apartment in another town on the coast, and I went there with him the first summer. I was 12, and already heavily into masturbating when I went there. Then, I had no friends, nothing to do, and a beach full of almost naked girls a block from my door. I spent all day masturbating.
Come time for bed, I have one more (or two more) orgasms before falling to sleep. But my dad was a few feet away. I would ever so slightly pinch and squeeze and scratch my tip and just below the tip...and lay there with erections "edging" like this, until the wee hours of the night. I got used to never making a sound. (This has proved useful for masturbating on trains, buses, at malls and all kinds of places).
Another summer my mom and I took a trip across country to visit relatives, and we shared motel rooms along the way. I'd take a shower and be the last into bed, and stroke myself to at least one climax, all the way from California to Florida.
Any one else do this?