Congratulations, Senator Stevens, but....

while the Senator from Alaska has become the longest serving Republican Senator (that is as a Republican - in total service Senator Thurmond exceeds him, but he served some of his 47 years in the Senate as a Democrat)

Senator Stevens has a long way to go to catch up with the long serving Democrats. If President pro tempore of the Senate, Robert Byrd were to announce his retirement today [unlikely - he was re-elected for 6 years just last November] - then Senator Stevens would need to serve beyond 3rd April 2017 to pass Senator Byrd's record. He would then be over 93 years old! But Senators Kennedy and Inouye are still ahead!

The days served are:-

Robert C. Byrd (D-W.Va.)* 17632 days
Strom Thurmond (D/R-S.C.) 17335 days
Edward Kennedy (D-Mass.)* 16228 days
Daniel Inouye (D-Hawaii)* 16171 days
Carl T. Hayden (D-Ariz.) 15281 days
John Stennis (D-Miss.) 15035 days
Ted Stevens (R-Alaska)* 13989 days
Ernest Hollings (D-S.C.) 13935 days
Richard Russell (D-Ga.) 13888 days
Russell Long (D-La.) 13882 days

* -- Still servingSource: Senate Historian