You pose a very interesting discussion. I did a little bit of research on it and apparently the amount of SST one does is largely dependent on your training goals. Some personal trainers and coaches will have their athletes doing SST daily in controlled amounts.
What you need to work from is TSS (Training Stress Score). Typically a well trained athlete can work with between a 500-700 weekly TSS score depending on recovery ability. 3 weeks on one week off (off week roughly 70% TSS of an on week). Sweet spot gives you a lot of bang for your TSS buck. The only problem is plateauing from not varying workouts enough.
Hi Steven and Jeff, thank you for the great link (read) and the hint with the TSS. I will look into that metric. Does Zwift show me the cumulated TSS? I guess not!? I would need StravaPro or add it in Garmin Connect!?