We turn the heat on 3 weeks after the air conditioning goes off. It's been consistently 3 weeks
We bought a 1200 sq ft house in '81, in '92 we added on 2400 sq ft, pus a garage.
The old and new have separate furnaces and air cond units. When our kids lived here, we ran both, but now that they are gone, we turn on the heat/air to the old part only when we know we will be in that part.(probably 4 days/week)
When we added on, both new and old got new windows, 2 x 6 instead of 2 x 4 outer walls, 30" on insulation in total attic, all outside walls have fiberglass insulation to fill 6" space, 1 1/2" styrofoam insulation, and Tyvec wrap (though I can't remember what went on first, it was in 1992). The new crawl space, and old basement are insulated in various ways.
(We're in NW Ohio. If you're a gardener, it used to be a Zone 5, but now they say a Zone 6)