Originally Posted by
carpediemracing
By definition if you hold a given power level for one hour and one second then you weren't at FTP. You should be absolutely wasted at one hour flat.
At least on the Wattage forum, Coggan's notion of FTP is considerably more fuzzy than that. If I have some time later today I can try to dig up some of his comments, but he generally takes a 40km TT as his reference (which should be ~ 1 hour for most people).