Sensor network generally detects target at a fixed frequency. Detection interval means time spacing between two adjacent detection attempts. While designing a sensor network for detection of target intrusion in a specific region, the interval should be carefully set with trade-off between power consumption and detection performance. This is because redundant power may be consumed if it is too short and the target may be missed if too long. In this paper, we study the determination of the maximum detection interval (MDI) with specified detection performance. Path exposure is adopted as a performance metric. For detection-oriented application, a novel method to evaluate the minimum path exposure (MPE) is developed. Then the MDI problem is formulated and its solution is presented. The factors influencing the MDI are extensively simulated.