White noise is not habit-forming in any medical sense, and there is no evidence that using it into toddlerhood causes harm. So the honest answer to "when should I stop" is: when it stops being useful, or when it becomes inconvenient.
That said, most families find a natural window somewhere between 12 and 24 months. The reason is practical rather than medical — the older a child gets, the more disruptive it becomes if they cannot sleep without it at a grandparent's house, on holiday, or at nursery.
Signs it may be time. Your child sleeps through household noise during naps without it. They fall asleep in the car or pram with no sound support. The machine is no longer making a noticeable difference to how quickly they settle.
How to wean. Do it gradually over two to three weeks rather than stopping abruptly:
- Reduce the volume by a small amount every few nights. Small enough that no single step is noticeable.
- Once it is very quiet, start turning it off after your child is asleep rather than leaving it on all night.
- Then move to turning it off at the point of settling.
- Finally, drop it entirely.
If sleep gets worse at any step, go back one level and hold there for a week before trying again. This is not a race.
Reasons to keep using it. Some households genuinely need it — thin walls, a noisy street, shift workers, siblings sharing a room. In those cases masking sound serves a real purpose and there is no reason to remove it just because of age. Keep it at a safe level and well away from the bed.
One thing worth avoiding: stopping abruptly during a sleep regression, a house move, teething, or an illness. Change one thing at a time. If the household is already unsettled, wait for a calm stretch.
Whatever age you stop, keep the volume around 50 dB and the source well away from the bed for as long as you use it.