Store your cake toppers away from:
I store mine in a cupboard.
Kitchen is not the best place for storing cake toppers due to the heat and high humidity, but if no other place is available, choose a cupboard that is away from the oven, dishwasher or other electric devices that generate heat.
Other places to avoid are the ones close to central heating and windows.
If your cake toppers have sticks, put them in cake dummies as shown in the photo below.