Here in Michigan, it's been bitterly cold for the last couple of days.
I have an automatic thermostat which I lower the house to 65 during the
day, and back up to 69-70 at 4:30 so it's warm by the time I get home
from work.

The problem is, it took FOREVER to get back to that temp last night.
When I first came home I thought my furnace wasn't working right (had
the ignitor replaced last week), but it was running... It just wasn't
getting warm.

I change the filter regularly, but I have a lot of windows in my
house...

So the question is, is it worth it (energy wise) to lower the temp
during the day, when it takes so long to get back up to temp? I'm
thinking I'm buring as much gas to bring it back up than I might save
during the day.