How do I effectively use the Pomodoro Timer feature in Study Ace to study for 3-hour exams?

I've been trying to implement the Pomodoro technique, but I get tired after 25-minute intervals and feel like I'm wasting time switching between focused and break sessions. I've also tried using a traditional timer, but it keeps me distracted from my notes. My exams are 3 hours long, and I'm struggling to stay focused and retain information, so I need a tailored approach to use Study Ace's Pomodoro timer.