We will always suggest you a specific watering schedule according to the plant species and terrarium type you've chosen and it is always attached together with the terrarium when we send them out😉 However, that is only a guide for you to start with, always adjust the watering schedule according to the environment you're providing.
Always water ONLY IF the soil is totally dried up. If you're putting them in aircond room or a windy spot (ie. balcony in high rise building), the soil tends to dry up faster and you may wanna water more frequently. If you're putting them indoor or at the car porch/backyard that barely get ventilation, reduce your watering frequency. Always observe the changes in succulents.
If they are thirsty, their leaves tend to shrink and you could see wrinkles on them. It's always safer to water only if you see wrinkles than to overwater them.