No way, you can't really say that because if you can sustain 235 watts for 60 minutes and then fade, then that's your FTP. I'm under the impression that the longer the effort, the slower the maximum power your body's capable of putting out drops. For instance, if you can give out 250 watts for your maximum over 60 minutes, then your maximum over 70 minutes would be somewhere around 245 and so forth. And since you can do 227.5 watts at 70 minutes "comfortably", I'm assuming you could sustain this for another half hour or something rather than completely cracking after 70 minutes at 232 watts. There is also the chance that you may be closer to 85% of your FTP at 227-235 watts now because you don't have any bonafide testing to back up your new FTP.
Thomas Davis