I thought about something that I've been doing for years well at least an aspect of it. Before we get to that, conventional wisdom has it that if you lock the dead bolt on your exterior door which can only be locked from the outside then you definitely won't forget your keys providing you had the wherewithal of keeping the house keys in your hand on the way out. That way you'll never lock yourself out. And when I take the elevator downstairs to check my mail in the lobby and plan to be right back, I just lock the door knob and leave the deadbolt unlocked.
However, when you're leaving for the day, is it necessary to also lock the door knob too along with the dead bolt? If people can break through the dead bolt, the less stronger door knob's lock won't keep them out either. What I'm getting at is that when you return home, you have to unlock both locks instead of only the dead bolt. Two locks instead of one. Yeah the same key operates the tumblers on both my door knob's lock and the dead bolt but still it seems like an unnecessary step. The door knob's lock doesn't really provide a second level of security.