What comes before a fall? Happily for me this turned out OK, but...
Climbing out at last from an especially cold and unwelcoming field, in the corner of my eye I thought I saw something on the panel of the 172 SP flash. A few seconds, and again - THE OIL WARNING LIGHT! And again, coming now in pulses. I leveled and started a turn back, finger hovering over the mic switch, "immediate return for landing". But as I scanned the instruments, the words never came. Oil pressure: completely normal (I'd flown 20 Hrs in this plane in the last 2 weeks, so knew what normal was). Temperature, RPM, power setting, rate of climb, etc all normal.
By now the warning light was continuous. It had only taken a few seconds to go there from brief flashes, but the pressure gauge had remained rock steady. No oil on the windscreen, no smell of overheating. Now I was ready to go downwind for an immediate landing. But I didn't. The idea of that inhospitable place, no engineer on field, really grumpy FBO. My next destination, with friendly FBO and engineer on site, was 2Hr away. Over a cold, hostile desert. Unaccountably, I carried on. "Pressure Switch", I said to myself, "I know about these things". All the indications remained rock solid and I continued, ignoring the red light glaring in my face (and carefully studying every possible landing site as the landscape dissapeared under the nose).
On landing, I consulted with the local engineer, who confirmed my diagnosis, and conferred with the chief engineer at my home base who concurred and authorised me to continue to my final destination, where an engineer would be ready to fit a replacement sender. After another 2 Hr of freezing cold and hostile terrain, I landed, parked at the engineer's hangar, and went to a hotel. That night, I did a bit of Internet research, wondering how common failures of these switches were. Common enough to have an AD in Australia it turned out, because: switch failure of itself was harmless enough, but it was caused by failure of the diaphragm. And the switch, full of high pressure oil, was mounted on top of the engine.
The result had been in flight fires. In an instant, my blood ran cold. My clever 'judgement' was based on knowing a little, but not enough.