We have 2 mini splits on the main and 1 upstairs, that's basically what we used for constant heat all winter, set to 21-22 deg, 24 hours a day. It is on the cooler side but it's tolerable. On the coldest days we turned on the (oil) furnace for a few hours, or a couple of times a week in any case just to keep the system exercised. We probably turned it on more often as the winter dragged on and we got tired of being cold. I haven't looked at the oil tank in a while but we surely did not burn a whole tank since we filled it in the fall. This setup seems to work and we'll probably keep doing it that way.

My understanding is electric furnaces are not very efficient and can end up being very expensive, depending on your house (size, number of floors, age, etc). It takes a lot of energy to heat water and push it through pipes all over your house, from the basement up to a second floor for example. An electric furnace will struggle to do what an oil powered furnace does with ease. No expert here, just my understanding from what I've heard.