It took me about an hour to actually write it, but I've spent ages sending it to people and making improvements since then. It's almost completely different to the one I originally wrote, because it changes a little each time someone else reads it.
Ten minutes. I'm one of those people who can just type something and it sounds fine. I finished all of my uni assignments within an hour this year, 2000 word essays, and I got As in them both!! Just that kind of person.