PostEaseLength should follow content, not the other way around
The more useful framing is not "what is the ideal length" but "how long does this piece of content need to make its point." Padding a thin idea out to hit a longer target hurts retention, since viewers notice when a video has stopped saying anything new. Cutting a rich topic short to fit a fashionable short length loses just as much.
Retention through the video matters more than raw length
A shorter video watched to the end generally signals more than a longer video most viewers abandon partway through. If retention consistently drops off at a similar point across several videos, that is a more useful signal about the right length for your specific content than a general rule borrowed from an unrelated channel.
Different platforms reward different lengths
A length that performs well on a short-form-first platform can underperform on one where longer, more developed content is the norm, and the reverse holds too. Match length to the norm of wherever a piece is posted, rather than using one fixed length everywhere.