Two or three nights interrupts the spiral and resets your sleep. Five to seven nights is where the deeper change tends to land. Answer four quick questions and this planner suggests a realistic length for what you actually need, not just the package that is cheapest.
This is guidance, not a rule. A retreat is the reset that lets you change the pattern at home; even a short break helps if a long one is genuinely out of reach. If burnout is affecting your health, speak to your GP or NHS 111 alongside any retreat.