To a limited degree it pays to close off parts of the house that don't need heat. I think you need to take this on a case-by-case basis.
I agree. I think the artticle said not to close off more than a certain percent of the house, or it would increase the workload on the furnace. That being said, the reverse is also true. As long as what you close off is less than that percentage, it will not harm the furnace & you will save money. Most people I know who do this do not close off the entire house. In the winter we use the vents in the rooms to decrease the air flow to the bedrooms upstairs in our split leve, because heat rises. In the summer, we decrease the air flow to the rooms on the bottom level , which are 1/2 below grade, because cold air falls. Doesn't seem to hurt the furnace at all, & we are decreasing flow to nearly 1/3 of the house.
I do find that simply setting the thermostat to 59 at night & 62 during the day saves a lot in the winter. Opening the blinds on our bay window when the sun is out uses the passive solar heat, & often raises the temp in the house to 68-69 degrees. We dress in layers, & it works for us.