Context first: the idea that a fixed travel duration alone determines traveling in low season for better prices is a bit simplistic.
Here in the UK, date flexibility is paramount, not just the number of days.
A two-week stay during summer school holidays will remain more expensive than a week in March, even if it's shorter, because the local demand is much higher.
Many people cannot choose their dates due to work constraints or children, making this "low season" theoretically inaccessible to them.