Does meditation session length matter?

The randomised evidence does not show that it does, within the range that has been tested. Six trials have assigned people to different session lengths, and none found a reliable advantage for longer sessions on mental health, wellbeing, affect or mindfulness outcomes. This is not proof that length is irrelevant, because most of these were superiority trials rather than equivalence trials, and several were small. Observational studies of self-selected practice sometimes do find associations with longer daily practice, but those cannot separate the effect of the dose from the characteristics of people who choose it.