I agree with REW that while you might save some, you would need to repeat the experiment under the same conditions, with and without the set back, instead of extrapolating from the above observations.
My own solution is much simpler: I leave the thermostat for the central air
fixed at 45degF year round, whether I am there or not.
Given your moderate temperature, you do not need heating at all.
OK, OK! I admit, I do have to change from Bermuda shorts into long pants. And we do use a space heater for the master bedroom, plus an electric blanket to keep warm.
Before you start to call us Mr & Mrs Scrooge, I will hasten to add that we have passive solar heating, which does heat up the interior to 70-80 degF in the late afternoon. But it is true that even in the winter, I need to sleep with a small fan blowing a light breeze on my face.