How Long Do Chanukah Candles Have To Be Lit?

How long do the Chanukah candles have to last? The Gemara (Shabbat 21b) says the Chanukah candles should be lit with enough fuel to last for the time from nightfall until the people leave the marketplace. The Rif (Shabbat 9b) explains that it was a half hour from nightfall until the people left the marketplace. This is the basis for Shulchan Aruch 672:2 and many achronim who write the one should make sure to have a half-hour’s worth of fuel. The question arises whether this amount of fuel should change depending on the modern world. The Ritva (21b s.v. Ad) points out that this amount of time is not an objective time period, but rather is dependent on the time and place. If so, now that people are out in the street until very late in the night, do we have to make sure that the candles stay light much longer? In fact, there is a well-known practice of the Griz of lighting with enough oil to last many hours into the night because nowadays there’s people who walk on the streets very late into the night. On the other hand, based on Rishonim, Chazon Ovadia (p. 66) writes that really a half-hour is a fixed period of time set by Chazal and doesn’t change over time. Alternatively, Rav Shternbuch says that we should light so that it should last as long as most stores are open and a lot of people are outside, but we don’t need to be concerned for the individuals who are ont he street all night.