I have a hobby called postcrossing (http://www.postcrossing.com/about). I am sending and receiving cards from all over the world. And I am so enthusiastic that I have two accounts: one for Helsinki (http://www.postcrossing.com/user/soikkis) and another one for Naantali address (http://www.postcrossing.com/user/soikka). I really enjoy this hobby. Sometimes senders are writing something about themselves, sometimes about their country and sometimes it is something else. Every card is surprise.
The nearest letter box here in Helsinki is about 150 meters from my rented flat. Another one is on my way to work. In Naantali nearest one is about half kilometer from my home. So I really know my nearest letter boxes and know the collection schedule.