I think this was originally because I was planning to go to the Burning Man festival, in which being covered with lights is a practical way of keeping track of your friends. But the idea was a bit beyond my expertise for a long time, and it took about two years before I found someone who said they would help me with the electronics side and I decided it was worth the risk of buying the kit to try.
I started work six weeks before Glade 2006, i.e. about June. I also optimistically hoped to finish something basic in time, but it took until about February 2007 before I had something which was self-contained and wearable. Obviously not all of this time was spent soldering LEDs, but soldering and testing those and about 400 wires was the biggest job.
Then progress stalled for a while, since I was a bit sick of LEDs at that point, but if I wanted to take it to Glade 2007 I needed to finish it off: some decent patterns and a button to switch between them, which I managed about 4 hours before having to get up again to catch the train there. And it was a success! Despite ridiculously heavy rain leading to a big mud bath at the festival, the hat did it’s job without breaking and the most common response was, “Wow, cool hat! Where did you buy it?”