I agree with Curtis. I've done a number of double centuries too (55 since my first in CA in '03), and I've seen Curtis riding along on a number of those! As for Stapfam's lot, it doesn't sound promising on the surface, but as others have noted, with the proper training (on several levels) 180 miles in a day is quite do-able.

I remember my first 180 (300K brevet) back in '82; turned out to be a lovely ride and got me started in the sport of ultra-cycling (though I was absolutely knackered at the finish!).

Rick / OCRR