Yeah, that’s exactly what I would expect as well. I think one can only reach a certain level with low volume. It is surprisingly good and effective as you note in your post, but at some point the rider will plateau and need either more or a new stimulus to further adaptation. What you’ve done is basically made your LV plan a MV plan.
My point was that if you made an LV Polarized plan, you’d have like one interval every two weeks. I cannot imagine that is enough of a stimulus for most people to generate the gains they would be looking for. Nate mentions the volume limitation in the below thread. There just has to be minimum cap on volume for Polarized to be effective, I would think, and 3.5 hours probably ain’t it.