Why wait until July? I think that most people train for IM the wrong way. Up until July I will be training the way I would for any season, A ton of intervals, biweekly 3-4 hour rides with tempo and 60mp pace thrown in. Quite a bit of racing. In general this will make a person the best cyclist they can be.
I've always been a believer in the fact that doing 5 hour slow rides, will make you really good at riding slow.
Recently on another forum someone stated the best way to train for IM is like a 40k time trialist until 6 weeks out. Jordan Rapp(a good pro triathlete) whole heartedly agreed.
Up until July instead of wearing myself out with 100-120 mile rides evey weekend I can be increasing my FTP(power I can put out for one hour) which is one of the key determiners of a cyclists overall ability. Once I hit July I will only need three or four practice runs where I am able to nail down my nutrition, pacing, and of course gear placement. The only way to improve your long distance speed, in long distances, is to really push the line on those long rides. The only problem is how fatiguing it is to not just ride long, but also hard.
I should state this is my first Ironman, but I also should say that I have talked with about 10 guys about this who have all gone between 9:30 and 10:30 and numerous more who thought they should have been able to be sub 11 and blew it. I would say the highest rate of success comes from people who prepare more in the last six-eight weeks leading up to the event. They haven't spent all year worrying about IM so their mentally prepared, they race more so they are in better shape, and finally, on race day they are more consistent because they don't do a big massive taper which is a huge hit or miss I believe.
I'm no coach, I'm not a fitness expert but I am a fan of the sport. I do believe I can hit my goal on race day and have no doubt that this training strategy is the way to do it.