Rabbi Yosef Chaim ben Eliyahu, Torah Lishma, section 76, (the Ben Ish Chai, a major halakhic authority of 19th century Iraq).

Question: There are people whose practice is to light seven lights before Shabbat evening [Friday night] and leave a great quantity of oil in them so that they will stay lit into the evening of Shabbat day [Saturday night]. They do the same as well on holidays. Is there a basis in Jewish law or a hint at such a practice in the teachings of the Sages? Let the teacher instruct us for righteousness and his merit will be from Heaven. Answer: Concerning the seven [lights] there is a basis of a hint in the holy books, but I did not find a basis or hint in the holy books for leaving a great quantity of oil in order that they will be lit for the entire Shabbat day into the evening [of Saturday night]. And I say that this practice is not commendable, and needs to be stopped, since it transgresses Bal Tashchit [do not destroy] since how will a light amidst light be helpful? The only place where it is appropriate for a light in the day is in synagogues, due to the honor of the synagogue, and not because one needs the light there, and so too for memorial lights for those who have departed. But [not so] lighting a lamp in one's home on Shabbat where the Shabbat lamp is for enjoying the light. During the day there is no enjoyment of the light [of this lamp]--why should one light it? And the Talmud in Tractate Shabbat p. 67 says, “One who covers an oil lamp or uncovers a kerosene lamp violates the prohibition of bal tashchit.” And based on this passage of the Talmud I taught to those people whose practice during weeknights is to place two wicks in an [oil] lamp in order to increase the light in the house. Their practice is to leave the lamp lit also during the time they are asleep, until the morning, since they need the light when they get up in the night from bed for whatever purpose, and it is difficult for them to get up in darkness. I instructed that they need to remove a wick at the time they are sleeping and leave just one wick lit, since at the time they are sleeping they do not need the increased light, and if there would be two wicks lit together the oil would go to waste, and there is here a violation of Bal Tashchit, as it says [in the Talmud] “one who covers an oil lamp or uncovers a kerosene lamp..” And there should be peace, and G-d, the Master of Legions, should help me. 1 The Ben Ish Chai seems to be writing in a community whose homes were built to provide natural lighting from the sun. [Translation by Rabbi Yonatan Neril]