We didn't change the water every time. The bottle warmer is easy to clean.

We always poured it away because of the limescale deposits.

We change the water every time as we have very calcareous water.
If we heat the water in it and leave it to stand, the appliance is already calcareous in the afternoon.

In the past, with the descaling system, we also left the water in and only washed it out in the evening.

No need to change the water regularly, the water evaporates after a while, adding more is enough and from time to time it needs cleaning (very good product).