NCIS is one of the best shows ever made in my opinion. The longevity of its greatness even with so many turn overs in cast speaks for itself. Usually when a show has so many cast member changes its the beginning of the end. It is so hard to find the right people to build the casts on screen relationships the first time but to be able to do it over and over is near impossible. I believe they have been so successful at this because they shift and mold the flow of the show to fit the new cast member. They don't bring in people to play the exact same part. They allow the actors to come in and build their characters with their own abilities and flaws. They make their own relationships within the story instead of trying to fill the impossible shoes of the past. It shows the strength of the writing and just everyone involved in making the show. From losing Sasha Alexander (Caitlin Todd) to bringing in Cote de Pablo (Ziva David) from losing Lauren Holly (Jenny Sheppard) to bringing in Rocky Carroll (Leon Vance). The dynamic changed but never faultered and you just don't see that very often. For me the hardest B cast member departure was Muse Watson (Mike Franks). Even though he was a recurring role and not a main cast member his relationship with Mark Harmon (LJGIBBS) couldn't have been played better by anyone else. He was Gibbs trainer, mentor and best friend. The two of them set their own rules and lived by them no matter what. They where both willing to cross certain lines to help, defend, and cover for each other no matter the personal cost. Mike Frank's is old school and believes woman are useless. Even though he will never fully change he does start to eventually soften on these views. First when Jenny Sheppard sacrifices herself to protect him and Gibbs from past retaliation. Second from the heart melting interactions of Abby Shuito (Pauley Perrette) who is Gibbs favorite and let's admit it just down right lovable starts to melt that heart of stone inside Frank's chest.
If you take the time to watch NCIS I believe you will feel the same way I do and will not regret a single second.