Each trial is as unique as the people involved, and there is no way to predict how long the trial you are chosen for will last. A trial can last a day or take two or three days. They are seldom much longer.
During the trial, the judge will tell you what time you need to be in court each day and what time to expect each day to end. You will also be given a break for lunch, which you may choose to take at one of the many restaurants around the courthouse. Please check with the Bailiff where these restaurants are located.