So, yeah. Zoe is awesome in her return to House of Cards. But, that doesn't necessarily mean she's going to come back time and time again for my personal pleasure. In fact, Kate Mara is only in the one episode of House of Cards Season 4.
Here are some numbers... After nearly 230 years, the US Senate has more than 1855 distinct former members. The term length for Senators is 6 years (compared with the typical length of 2 years for representatives). Here is the histogram of term durations for all past Senators. Note: some people served multiple, non-consecutive terms, or changed parties, which counts in this data as a separate term. You can clearly see the spikes of 1, 2, ... 6 terms. The average term is 7.6 years (median 6 years) for all past Senators.
U.S. Senators serve 6-year terms, and can serve unlimited number of terms. Senatorial elections are held every two years, with 33 or 34 seats up for election each two years, in a rotation. So if you start with 100 Senators, you have 33 up for reelection in 2018, 33 more in 2020, and 34 in 2022 (Iâm not sure which year actually has 34 seats up for grabs, but you get the gist, I hope).