If you get a lot of blowing snow sucked into your outdoor coil, you could require some aux heating.
While your system does it's defrosting cycle(s).
If I think that there is a chance that back-up heat will be needed, I'll pre-set my
oil heat thermostat a bit below the Sanyo's lowest setting. It's a set and forget..
One thing I have done when I know it's going down near zero, is put my hotwater baseboards in free-flow mode.
The thumb screw on top allows boiler water to flow upstairs to the baseboards.
If I use just 3 turns up, the flow is very slow, so the percentage of contribution by burning oil isn't very high.
So, it keeps down the burner run-time.
The problem of my centrally located Sanyo not keeping distant rooms
warm as the living room is
gone during Hybrid mode..
And of course when it's super cold outdoors, that's when my north facing den
(with less insulation and loads of glass) wants to cool down the most.
I will be adding more insulation next year. Storms over the 4 sliders
and more foam underneath.