No, never. The back door is a stable door. Always left unlocked, and mostly at night too as I just forget.
The front door is pulled closed and that's it. I never double-lock it with the key.
I feel very safe where we live, even though we live on a busy little street (pedestrian busy) just off the highstreet of a big village. So lots of passersby during the day, and even at night as the village boasts a large number of restaurants.
My main fear is burning to death in a house I have protected so well from intruders that I am unable to easily get out.