Periodization on three hours a week (and why a blog is a bad thing)

As i struggle to feel as though i'm adequately preparing for the arrowhead bike race (even though it's still a long way off) i end up thinking a lot about how best to schedule my workouts while keeping to the three hours a week.  it's actually a bit ironic - although i'm technically exercising only 3 hours a week, the whole effort takes significantly more time than this.  Partly because it probably needs too - there is a lot to consider in order to optimize the time - and partly because it's a means of procrastination.  This blog tends to make it worse - i like writing down my ideas so much that i'm starting to post instead of working on my thesis.  This has got to stop, at least eventually....

I also spend some time thinking about scheduling in an effort to make Dave's workouts as efficient as possible.  One thing i've been turning over in my mind recently is how to best introduce 'periodization' into this program.  it's pretty easy (i've found) to improve handily in a discipline just by doing a fairly balanced, unperiodized set of workouts that incorporate moderate to high intensity efforts.  This is most of what i've done over the past 6 months - one speed, one tempo, and one 'endurance' workout a week - always changing to avoid boredom - with the disciplines changing at least once a week (ie never 3 run workouts in a single week).  But as i'm gearing up for a bike race that is probably going to take me anywhere from 20-40 hours, it's clear that a bunch of one hour workouts is going to potentially leave me underprepared.  I say potentially because the arrowhead will not be a 'fast' race - the environmental and logistical limits that will present themselves with likely determine an optimum speed, which will likely be one at which even my present fitness will see me through.  My proposed ironman however, is another story.  if i want to stand a chance of getting top 25% i'll need to be able to 'push' moderately hard for 12 or more hours.  how do i do this when thats all i train in a month?

I've had a couple ideas.  Joe Friel's 'build' phases in his Triathlon training bible are characterized by 4 week blocks where the first three weeks have increasing volume and the fourth week is kind of a 'recovery week'.  splitting six hours over each to weeks, i can easily emulate this.  for example:

•  week one (2.5 hours)
•  a 1  hour bike
•  one hour run (both with tempo intervals, for example) 
•  half an hour swim.  
• week two (3.5 hours) 
•  30 min run
•  30 min bike (both with speed work)
•  15 min swim
•  45 min bike (race pace or greater) followed by 90 min run
•  week 3 (4.5 hours)
• 30 min run (easy/moderate) or even swim
• 40 min bike (tempo/tt) - much faster than race pace.
• 3 hour ride (race pace) followed by 20 min run (race pace)
• week 4 (1.5 hours)
• 30 min bike (easy/moderate)
• 15 min swim (race pace)
• 45 min run (moderate, race pace)

This schedule could be followed the next month by something similar, but with the weeks using 2, 4, 5, and 1 hours to allow for slightly longer 'long' workouts.  Keep in mind that this schedule is based on the fact that i'm a decent swimmer and won't be working much on swimming prior to my race - other than trying to make sure i have a good 'water feel'.  of the 12 hours, 6:25 is spent riding, 4:35 running (or 4:05), and 1 hr (or 1:30)  swimming.  Interestingly enough, looking at this, it appears that these ratios are roughly what i'd hope to be doing in an iron distance event.