You say potato, I say po tat o 
I think of the time trial as a measure of fitness, at max effort.
Time and pacing are good data to measure, understanding environmental variables.
But most important thing that the time trial represents, is your fitness at max effort irrespective of pacing
Can you go effort hard, and how long can you sustain?
For this your Heart Rate data and ability to effort at and above your lactate threshold will show your "fitness" level
Measured at 4 or 5 week intervals this data will indicate how your training is coming along.
If a race is the definition of a hard effort, we would seek to build a strong base of fitness with that as the goal.
Design a plan to "Build" and increase Zippy's level of fitness, and then like a good project manager...
We would test the turtle periodically to make sure we are moving the green monster along.
You must start using your HR data at your different effort levels for this insight.
What is an easy, lower HR that you can maintain over a long period (Think Long Slow run, easy bike, easy swim)? "
Where is your HR at the middle level of effort, your having an endurance effort (Think of this as difficult, but I can sustain for a while) "just below Lactate Threshold"
What is your HR at the perceived hard level of effort (This is hard, I can do this for a little while, but I know my walk break better come soon) This hurts - You are above your LT, the clock is running
The data about your LT continues to grow showing that this is less age specific and it is easier to improve than your VO2 max which is quite age and genetically limited.
You cannot always train at hard efforts, you will break down and lower fitness will result.
For the biggest gains think the 80/20 or 70/30 rule:
80% of zippy's workouts should be at the Easy or Endurance effort levels (just below LT) to build a base
20% of the workouts should be hard (at and above your LT, fartlek or hard interval workouts) these encourage your body to increase LT
To round it all out:
You can get specific with your Heart Rate and assign and determine number ranges for the effort levels
OR many turtles just use and know their perceived effort levels:
EASY
ENDURANCE (Below your LT still aerobic)
HARD (At or above your LT close to the limit or anaerobic)
So thinking about your running as an example the 80/20 balance over a 10 or 11 day period could go like this:
Day 1, EASY, 2 to 4 mile run just find an easy pace and put in the miles
Day 2 No run
Day 3, ENDURANCE run, don't go anaerobic, but push your effort
Day 4 No Run
Day 5, EASY run
Day 6 No Run
Day 7 HARD 3-4 mile run, aggressive intervals, ladders
Day 8, No Run
Day 9, No Run
Day 10 ENDURANCE run
Day 11,No run
Wash rinse and repeat
You could do this cycle in more days or less, but try not to run on back to back days (Increased chance of injury)
Sorry for the length of this post but I wanted to illustrate
