I'm not sure I'd agree with the erm's advice. We both owned MKII diesel Octys. Mine is still as good as new whereas the erm got rid of his having spent years referring to it as Satan's Wheelbarrow. Mine has never had anything other than diesel in the fuel tank and has it's oil changed every 20,000 kilos which is a little ahead of manufacturer specifications (on variable service it'd go somewhere between 25,472 kilos and 30,000 kilos before asking for an oil change). The important thing is to follow manufacturer specifications for both time/distance between oil changes and oil specification. 92% of engine wear / oil deterioration occurs when the engine is cold. I doubt your engine ever cools down, Ken!
I would agree with checking the oil level periodically. I check mine on the first weekend of every month. The MKII (with over 360,000 kilos and only 1 clutch change) is good as gold and never consumes oil. The MKIII, on the other hand, tends to need half a litre or thereabouts every second or third month. I believe the oil consumption is normal for that particular engine, being caused by periodic automatic DPF regenerations. Anyway, don't rely on the light to tell you if/when a top up is required. They tend to go well below the min level before the light comes into play so get into the habit of checking it regularly (whether through diagnostics interrogation, through the infotainment system or with the dipstick)... along with topping up screen wash and having a quick glance at brake fluid and coolant levels and check the condition of your tyres. In fact most of that is covered in Lesson 1 of RSAs Essential Driver Training course. As a qualified and registered ADI I would be happy to book you in for a lesson, if required.