What you should say is butter lamp. Butter lamps usually depend on their capacity and wick size, so their duration is different. For example, the butter lamp holder provided by my family is relatively small, and it is generally necessary to refuel and change the wick after two days. There is a big lamp holder in the courtyard of the Great Temple in Tibet. It may take two weeks to replace it. However, the big lamp holder in front of the Buddha is the main lamp holder of the temple. It is guarded by a special Lama and will be filled with ghee every half an hour or an hour, so it will never be erased.