Worst case, you have to use a key. It would be the same with a conventional door lock.
__________________ Ren: Now listen, Cadet. I've got a job for you. See this button? Ren: Don't touch it! It's the History Eraser button, you fool! Stimpy: So what'll happen? Ren: That's just it. We don't know. Maybe something bad, maybe something good. I guess we'll never know, 'cause you're going to guard it. You won't touch it, will you?
I have key pad entry on the deadbolt only. Door knob does not lock. I used to fix doors after break in s and realize that both locking is not needed. If they break in the deadbolt the locking knob is not going to stop them!
The batteries last over a year and if you change them say every 6 months should not be a problem. As other poster said you should have a key as back-up. I actually do not have a key for the key pad, but for the other door if needed.