The packet-switched on-chip interconnection networks are emerging as the pervasive communication fabric to connect different processing elements in multi/many-core chips. As a preferred NoC flow control mechanism, Express Virtual Channel (EVC) allows packets to virtually bypass intermediate nodes to minimize communication delay. Technology scaling results in process variation and Negative Biased Temperature Instability (NBTI) which can significantly affect the reliability and lifetime of NoC fabricated using nano-meter transistors. In this paper, we propose techniques that significantly improve the reliability of both static and dynamic EVC-based NoCs by reducing the simultaneous impact of process variation and NBTI. Our evaluation results using a detailed cycle-accurate simulator on a wide range of synthetic traffics and parallel benchmark traces show up to 74.2% (75.5%) guardband improvement over the conventional static (dynamic) EVC-based NoCs.