The long-term congressional staffer is the exception not the rule, no?
Back in the days when I looked at political trade papers more than I do now it seemed there were a lot of turnovers in Congressional staff every week. Of course they didn’t list the entire staff size so I’m really not sure.
You have the senior congressional staffers who make a career of bouncing from Congress critter to Congress critter, and then you have the short-term staffers and interns who might work a year before moving on. And then there are the sectaries and office managers who wield the real power...