What is the etiquette for holding the door for people?

Let’s say we’re talking about your work building, and the people that you may or may not hold the door for are not carrying large boxes.

How far from the door do they need to be when you walk in for you not to hold the door for them? I feel like there is this weird limbo area between 10 and 20 feet, in which I awkwardly can never decide if I am supposed to hold the door for someone. If the person is less than 10 feet behind me, sure, I’ll hold it (otherwise it would shut right before their face). But what if they’re 10–20 feet away? Especially 20 feet away, I feel like it’s overkill to hold the door that long. (It’s not like it’s that hard to open…) Of course, if they were carrying something heavy, I would do so, but otherwise, no.

What do you think? When do you, and when do you not, hold the door for people? Do you ever feel awkward in deciding when to do so? Has someone ever not held the door for you, and you thought it was rude?

Discuss everything about door-holding etiquette, please.