Research on deliberate practice and attentional performance supports 60–90 minutes as the optimal single deep work block. This is long enough to allow genuine cognitive immersion (the first 15–20 minutes of any focused session involve the re-establishment of deep concentration — the productive window is in the middle), and short enough to maintain quality without significant performance degradation from attentional fatigue. Start with one 60-minute session per day and expand to two when the single session is consistently productive. The limiting factor is not time available — it is the combination of distraction reduction and attentional recovery that makes each session genuinely productive.