It was early morning, close to 5 AM when Sarah and Aiden approached the main base of the poachers with their group.
They decided on an early start because it is a high probability that the poachers will still be sleeping or just waking up and their alertness will be low. Also, most of them should be in the base before they go to check the traps or whatever other tasks they have. Sarah and Aiden want to reduce the risk of being caught off guard by poachers who are returning to the base.
While on the topic of other poachers, the sooner they attack, the smaller is the risk that these guys will be alerted of the happenings in the other two bases from the previous day.