The main requirement of Industrial Internet of Things (IIoT) is reliability with a targeted reliability of above 99.999%. Then come latency and energy-efficiency requirements. The next step for the IIoT is to target time-critical applications. Even if IIoT technologies are now adopted worldwide, challenges remain and some of the limits of the technologies are still not fully understood. In this paper, we address TSCH-based (Time Slotted Channel Hopping) Wireless Sensor Networks and study their latency and lifetime limits under real-world conditions. We compute theoretical bounds on the end-to-end latency in a perfect radio environment and then in real deployments with unreliable links. We compare the performance of different scheduling algorithms and evaluate the impact of unreliable links on end-to-end latency and network lifetime, by means of simulations using traces collected from real deployed TSCH networks.