Yes, the test is long and could tire your brain. But here are a few things you could try
- take that optional 8 min break between math and english. Pace yourself, maybe snack on something
- While reading the passages, instead of thinking that they are long and boring, personalize them! Get into the shoes of the author and think like him. If he is happy, get happy with him. If he is protesting, think of ways to help him. This might come in handy on CR questions when you have to assume, or strengthen.
The only way to increase your stamina is to sit through more long hours so you get used to them. In no time, you will be able to focus and get through the last 75 mins.
Kudos if I helped