How do I keep the high efficiency in non exam week? My efficiency is very high during exam week. How do I keep this high efficiency at other times?
You probably can't.

Exam periods are high intensity last minute sprints, exhausting and taking a toll on the other aspects of your life. Personally, I barely spent time cooking or meeting friends. My time was spent on life support activities (eat and sleep), studying, and regretting not having managed my time better. I also remember being exhausted and not being able to do much intellectual work right after the exams were over.

You can pull this off for a short period of time, but you cannot keep this for long without being burned out. Plan ahead, spread your workload, and make sure you get enough rest and leisure to keep your brain rested and at peak efficiency.