In general, it takes somewhere between 10 to 14 hours for halved grape and cherry tomatoes to dehydrate. The actual time will depend on several factors, such as: • temperature of the dehydrator • humidity in the room • whether the dehydrator has a circulating fan or not to keep the heat evenly distributed • how often the dehydrator is opened, and if it opens from the top or side • size and moisture content of the tomatoes • whether you are drying until moist-dry or leathery-dry