There is that too.Glad you liked it too. Keep in mind that his suggested paces presume training at the distances for which the paces are given:
"Do keep in mind that a 5K runner is unlikely to run the equivalent time in the marathon off of 5K training. The runner would obviously need to train for the marathon to accomplish this equivalent time."
So for example, if I can run a mile in 7:40, I should be able to run a half mary in a little over two hours, according to McMillian's formula. But I can't really, because I haven't worked up to that distance yet. I would imagine I would have to run 12-15 miles once a week for several months before my mile time would translate well into my half marathon time.
BTW, I'm also thinking about a half marathon in April or May next year, if I can make good progress in the meantime. Right now my farthest run is 8-9 miles, but it's a bit of a strain on my left knee, so I think I need to back down a bit for a while before I try to push distance again. Good luck on your training!
However, I was thinking more of the suggested training paces, which it was my understanding are the paces I should be running at now during my training runs. He even suggests updating your numbers in the pace calculator every 6-8 weeks so as to ensure your training paces are updated in line with your progress. Taking the long run pace as an example, right now I could not keep that pace up for more than 15-20mins without my HR going above 70% of MaxHR. Yet he suggests long runs should be a minimum of 1.5 hours.
I think it will just be a matter of improving my endurance(I have been working almost exclusively on bettering my 5km time lately) and trying to get a more accurate idea of my MaxHR. I might find I have a higher than normal MaxHR and what my HR is at the suggested pace is actually close to 70% of my MaxHR. Failing that, improving my endurance will mean I can keep the pace up longer. So either way I'll come out ahead.