I’ve gone sub 4:00 both in the build up to a full distance (starting tired, but big form), on the afterburners after a full distance (starting really fresh, but less form) and as a A-race for itself (fresh and with big form).
Training average for me (excluding 3-4 weeks of offseason) is 17-18 hours, but this is average for the 11 remaining months of the year. Bigger weeks around 28-30 hours, but a normal week is 16 hours. Swimming x3-4, bike x5 and running x6 - 12-15k in the pool (SCM and LCM), 9-10 hours on the bike and 50-60k running.
FOP swim - swim courses vary but between 23 and 27 minutes for my sub 4:00
3x10x100 scm @1:30 hitting 1:14-1:16 with lactate below 3.0 mmol.
10x400 scm @6:00 building from 5:30 to 4:45 - lactate will be above threshold in the end.
Every second week I swim 60 minutes with no stops around 1:20-1:22 scm.
I would swim hard 1,5 times every week (I have my son every second weekend = I’m training 12/2, with 12 days “on” and 2 days with almost no training)
Bike - 2:04-2:07 on 290-300w AVG (81 kg)
Hour of power on the turbo between 320-350w depending on freshness in the legs
4x40 minutes outside in TT around 275w - staying below 1.5 mmol.
Everything between 6x5 minutes to 5x12 minutes on the turbo between 300 and 360 - staying below 2.9 mmol.
As much time around 230-260w as I can without killing the rest of the workouts
Run - 1:18-1:21
Most runs are basic runs between 7:20 and 8:00 minutes pr mile.
Threshold runs are normally also “long run” when I’m not training for a full distance.
I’m injury prone = threshold are more LT1 style than LT2, and I rarely go above 1.8 mmol in training.
Normally I switch every week between 5-6 x mile a little faster than 70.3 racepace, but staying below 1.8 mmol and the other week is 3-4 x 3-4k a little slower than 70.3 race pace.
My weekly long run is “always” 1 run longer than 20k, sometimes up to 24k in the build for a 70.3 (I don’t find this really important) and weekly milage is 50-60k. I really hope to build this to 65-70k this winter.
Bike really about LT1?
“Yes” - building LT1 is great, if it’s a limiter for you. When I’m race ready my LT1 is a low percentage of my LT2, which indicates that this could be a limiter for me. 285w LT1 and 345w LT2 - I’m working on getting a higher LT1, and with the training hours I bet my LT2 will also come up. Coming from a swim background I don’t find my VO2max a limiter… Not yet 
I don’t know with my mile time, being injury prone I don’t test this. But I can run X x 1k with lactate below 3.0 mmol in 3:30 pace. 400m free in SCM all out around 4:30-4:34. “FTP” around 4.4-4.5 w/kg.
I know I’m in shape for my 70.3 when I can do (with fatigue):
3x40 minutes @270w feeling GOOD
Swim 3x10x100 @1:30 hitting 1:14-1:16 feeling GOOD
Run 3x4k @3:50 min/km feeling GOOD
The thing you’re not asking… How many grams of carbs can you take on riding 70.3 pace in your aeroposition?
I drink 260-280 grams of carbs on the bike during a 70.3.