An appliance fault may need a quick response, and people who are asleep may not notice smoke, leaking water or abnormal operation promptly. Programme timers do not remove that risk.
Understanding this situation
Electrical Safety First advises against leaving washing machines operating unattended or during sleep. A previous history of reliable cycles is not a guarantee about the next one, and a long programme should be planned accordingly.
A useful next step
Choose a time when someone can remain available and respond to an unusual event. Keep relevant safety alarms maintained according to their own instructions. If a machine already shows a concerning symptom, do not schedule an overnight cycle as a way of avoiding the disturbance.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.