Thirty years ago I was the most junior birdman at a large Piper dealer/distributor. The boss wanted all the inventory flown 1/2 hour each month, and in the middle of a south Alabama summer I didn't need to fight anybody for the free flight time. I would do all the singles and one of the distributor demo pilots would do the twins. Lots of preflight inspections, lots of hot airplanes. When I got mine done I'd go help with the twins, which took more time. More engines, more avionics, more things to check, preflight and inflight. And I needed the experience.
One hot evening I walked up to a Seminole just as the demo guy was climbing aboard. I jumped in, strapped in, and asked him how the preflight went. He said fine, no squawks, and showed me the pitot cover. So off we go. A mile or two south of the airport the engine on my side gave a ladylike cough, then quit stone dead just like it ran out of fuel.....yeah, exactly like it ran out of fuel. I leaned over to study the fuel quantity gauges, and sure enough, the right one pointed at "empty."
He never did a preflight, or at least he never bothered to look in the tanks. He was too hot, too tired, and it was his last airplane of the day. The right quick drain had a slow drippy leak, and in a month's time all the fuel had disappeared.....all but the few gallons which got us to 1500 feet.
Good lesson for a junior birdman. Should we go flying together, please don't be insulted if I preflight your airplane, even if you just did. I'm not picking at it. I just figure everyone is human, even senior aviators.