You can, but it is not necessary. You can put the candle out after the thirteen minutes and relight it the next day. This symbolizes your ancestors' drinking. You may do it any time of the day or night. Within our belief system there are occasions for performing worship for three days, fourteen days, seventeen days, and twenty-one days.
Theses are specific and highly esoteric reasons.
Ninety-nine percent of the time, seven days is the correct number. You don't even have to have a formal shrine. All you need is the water, candle, and your prayers. If you leave during the course of the seven days, simply continue the sequence wherever you are staying. Be sure to adjust the time to when you were doing it at home.