My dad does it, lost of people do it.

They don't empty (archive) their in-box.

The time this wastes over your email life is HUGE. Think about it... the times you scan that inbox. Up and down. Reading and rereading.

I always try to practice GTD, but, like Buddha's Dharma, it's hard, but one of the four noble truths of GTD is surely to empty your in trey. Your-in box is your in tray.

Time is the most valuable resource.

If you empty your in-tray regularly then over your lifetime you could save over 4 hours of your life (That's equivalent to 80 cigarettes).