In yours maybe. In mine there's at microwave/regular oven combo which I use as an oven only when cooking cakes and pies or the odd dish requiring it. Electric stove for rumsteaks and pastas. The rest is microwave, microwave, microwave, cooking all sorts of liquids and vegetables. It is so much more energy and water efficient.
If you want to be energy-efficient, keep food hot by insulating it, not by continuing to heat it. Like in a hooikist. I can "soft-boil" a couple of eggs with a liter of nearly-boiling water from my hot-water heater, left in a thermos for half an hour.
Not unless you've sterilized it first. But putting food in an insulated container will only prolong its time in the zone between 40°F and 140°F if the temperature outside the insulated container is outside of that range. For example, if the insulated container is in a refrigerator, in an oven, on top of a cooking fire, or in a blizzard. So taken at face value, your advice is rarely applicable.
However, not all of that zone is equivalent! If your non-sterile food stays at 100°F for a long period of time, its decay rate will be much, much higher than if you keep it at 60°F. So a generalization of your advice is often applicable.
Which is precisely my use case. Me and my wife often eat small meals, sometimes even different for each of us. Many a time only one of us is at home for lunch and sometimes even for dinner.
Even when we cook larger quantities the 'traditional way' we end up heating them again the next day. Besides it's just outrageous to boil half a teapot for a singe tea cup when just filling the cup and popping it into the microwave.
When cooking vegetables with steam in the microwave we use a (provided) accessory with which you lay vegetables on a grid, fill the bottom with one glass of water, cover with a metallic lid and throw in a few minutes of power. A pressure cooker requires more water, a longer heat up time and a longer cooking time. It is also extremely bulky. We have one but never use it.
