Creative Marathons - Your experiences?

I've been reading recently about the concept of "Creative Marathons", where a group of people get together to create in a single place for a set period, usually 5 or 6 hours or more.

Intrigued by the idea, I tried my own personal Creative Writing Marathon, and sat from 8am to 1pm working on a novel at my computer, pretty much non-stop.

It was an interesting experience, and I found it surprisingly easy to write for so long but didn't worry too much about the structure of the story, I just wrote.

The last hour was more of a strain though and I was relieved to finish.

I had no expectations, and reading back what I'd written the next day, some was of more use than other parts.

But just by having that length of time set apart to create and do nothing else but create meant I could get into a different flow, and go to a different depth, than if I'd written for 1 hour on 5 separate occasions.

Have you ever been a part of any Creative Marathons yourself?

It'd be great to hear your experiences and thoughts on the concept, share your comments below.