LEL 2013 / London - Edinburgh - London Audax

I'm in for DecaIronman in September, in two minds over whether this would be an awesome last big bike training session or if recovery could be a problem.

For those who've done it (or similarly long audaxes), how long have you taken to get back to normal fitness-wise?

If wikipedia is to be believed, decaIronman = 10xIronman.

How on earth is it possible to run 262 miles immediately after finishing a ride equal to LEL? And surely if you are contemplating such lunacy you have some prior experience at this kind of thing, no?

Even the concept of a ten-times distance Ironman scares me.