If not properly taken care of, wood is quite easily prone to changes. Direct sunlight, heat and humidity will affect it most, therefore, it would be convenient to take the following measures:
Try to reduce exposure to direct sunlight to a minimum
Never put the wooden object on top of a heat source: heaters, radiators, etc.
Recommended temperature: 5ºC-30ºC
Recommended relative humidity: 60%-80%

To clean the figures, rub them with a dry woollen or linnen cloth and they will acquire a beautiful natural patina.