Grapefruit has an incredible shelf life and can last for an extended period of time in the refrigerator. According to a study performed by scientists at Rutgers University, fresh grapefruits can remain fresh for up to 6 weeks when stored in optimal conditions. When storing grapefruit in the fridge, it is best to keep them away from other fruits or vegetables emitting ethylene gas as this can speed up their spoiling process. It is also essential to make sure they are properly sealed and placed on a lower level shelf where temperatures are consistent between 40°F–45°F (4°C-7°C). Additionally, it's advised not to cut your grapefruits until you're ready to consume them, as doing so could cause them to spoil more quickly. Once you have opened your grapefruit, you'll want to consume it within 2 – 4 days after opening (unless otherwise specified on its packaging). If handled correctly and with proper care taken during storage, you should be able to enjoy plenty of juicy and delicious grapefruit even after spending some time in your refrigerator!