In its second season, NCIS refined its look and pacing, delved into its characters, and went beyond the military angle. I can't watch the DVDs, of course, without thinking of Sasha Alexander's end-of-season departure.
What if Sasha hadn't been overwhelmed by the hours? What if she could have seen herself playing Caitlin Todd for the long haul? Bottom line, she was overwhelmed; she wanted time to do other things. Both she and the show have moved on.