I honestly almost never answer my landline because most people I want to talk to won't call me on it. When I was at school, I'd answer my landline between 2pm and 8pm. I pick up my cell whenever I'm awake. The thing about cellphones is that you can turn them off/set them to silent, and they are often quieter than landlines when they ring, so I think rules are less strict about them.

At work, I have to call people to let them know their parts are in, and I won't start calling until 9:30am. The people I work with think that's strange.