Anecdotally from some meditation lineages—and from examining self report data from roughly 200 meditation practitioners—there seems to be a bump in meditation quality that happens after 40 to 45 minutes of sitting on the cushion so I would recommend you aim for 1 hour/day.
When reading reports like this it’s worth to be specific about what’s meant with “meditation quality”. Meditating that long gets you into different states. Those states are helpful if the goal is to have spiritual experiences. They also make it more likely to have some negative effects.
My prediction (based on a bunch of informal theory) would be that those states are less valuable when your goal is to train attention and the style in which I train recommends to not go over 20 minutes for beginners who have trouble holding focus anyway.
When reading reports like this it’s worth to be specific about what’s meant with “meditation quality”. Meditating that long gets you into different states. Those states are helpful if the goal is to have spiritual experiences. They also make it more likely to have some negative effects.
My prediction (based on a bunch of informal theory) would be that those states are less valuable when your goal is to train attention and the style in which I train recommends to not go over 20 minutes for beginners who have trouble holding focus anyway.