While binge-watching an entire series can typically be done in a couple of long nights or weekends, watching the whole gamut of NCIS shows would take much longer than that. The original NCIS series has been on air since 2003 and has 21 seasons. In season 21, the franchise celebrated the 1000th episode of NCIS between the flagship and its spinoff series. The 1000 NCIS episodes comprise NCIS, NCIS: Los Angeles, NCIS: New Orleans, NCIS: Hawai’i, and NCIS: Sydney. With so many shows to watch, fully experiencing the franchise is a serious investment.