Whether or not your students get up and wait at the door may not seem like a big deal. You're right. It's not. But little things can make a difference.
I am not a fan of having students sit and wait for the period to end because it creates tension. Students will inevitably start bothering each other when this happens. Then it becomes a game of saying "stop it" again and again until it's time to go.
Save yourself the hassle and have your students stay seated until the period ends. It will help keep things a little more orderly and less stressful for you.
Your students will be the ones who benefit.