Recognition is a memory skill, and memory answers to spacing far more than it answers to hours. Ten minutes on five days will beat fifty minutes on one, and the gap is not small. This matters here more than in most kinds of practice, because a drill round takes seconds — the temptation is to grind, and grinding is the least efficient thing you can do with the time.
A week that works
Five sessions of eight to twelve minutes, on non-consecutive days where you can manage it. Start each session with one level you already own — it is a warm-up, not a test — then spend most of the time on the level that is currently uncomfortable, and finish with a short mixed round so nothing gets practised only in isolation.
When to add a level
When the current one is boring, not when it is perfect. Chasing the last few percent of accuracy on a level you already recognise instantly costs more attention than it returns; the answers that are still wrong at that point are usually one specific two-way confusion, and the cure for those is a targeted round against the confusion set, not another hundred general rounds.
When to go back
When your errors stop clustering. A tidy confusion set — one neighbour, over and over — means the level is doing its job. Errors scattered across unrelated answers mean the level is above you and you are guessing, and guessing practises guessing. Drop a tier, get the errors clustering again, and climb back. Your progress page is where that pattern is visible.
The daily round is not a session
The daily round is one question. It exists to remove the decision about what to practise, not to be the practice, and it is deliberately too small to feel like an obligation. Answer it, notice what it was, and either let it set the theme for a real session or close the tab — both are correct uses.
If you only ever do the daily round, you will still be better off than not doing it, and you will improve much more slowly than someone doing three proper sessions a week. That is worth knowing before you build the habit around it.
Stopping well
End while you are still getting things right. A session that finishes on a run of correct answers leaves a different memory from one that finishes on frustration, and the difference shows up in whether you come back on Thursday. Ten good minutes and a clean stop beats twenty minutes and a bad mood, every week, forever.