Since 1970, the average time to fill the 15 Supreme Court vacancies that have occurred has been 55 days, far shorter than the minimum time it will take for the Senate to fill the late Antonin Scalia's seat if the upper chamber waits for the next president (342 days minimum).
Part of this is because retiring justices have made the confirmation of a successor a contingency on their retirement -- the only real waits have come from seats filled because of a justice's death.
While we live in a hyper-partisan era of American politics, 19th century vacancies generally took much longer than any other period in American history -- often because of various extreme partisanship (including the Civil War) making compromise impossible.
Justice Henry Baldwin died in 1844, but the absolute hatred between President Tyler and Whigs controlling the Senate (his own former party--though expelled) kept the seat vacant until the next presidency, making it the longest vacancy at 841 days.
President Lincoln didn't have problems with the Senate, the 37th Congress was dominated by Republicans (61 percent in the Senate), but he sat on nominating three vacancies -- two from death and one Civil War resignation --for over a year.
It takes 5 members of the Supreme Court to form a quorum. At times, because of the failing health of other justices, the court could not even meet because of a lack of quorum.
It's not completely evident why Lincoln waited, especially since many of his war-time orders and practices eventually worked their way up to SCOTUS -- having it loaded with sympathetic justices would have helped his own cause. Possibly he waited until there was simply no chance for reconciliation between the North and South, not wanting to antagonize the situation any more than needed.
When Chief Justice Salmon Chase died, President Grant was left with a conundrum. It seemed like nobody wanted the job. His first three offers were turned down, then the Senate rejected several more.
Grant was left with nominating a political 'nobody,' so much of a nobody that a former Navy secretary quipped, "It is a wonder that Grant did not pick up some old acquaintance, who was a stage driver or bartender for the place."
Even with all the troubles, the seat only stayed vacant for 301 days.
Only 72 days into the wait on Justice Scalia's replacement, it's not been a completely popular or consequence-free political tactic.
Almost all votes are coming down to Justice Kennedy's crucial swing vote, so far siding with the liberal justices in the majority of cases. Essentially, they have placed the entire power of SCOTUS in the hands of the most moderate member of the bench.
With the balance of power in the hands of a moderate, the court has handed down some significant losses to businesses. Dow Chemical, for instance, chose to settle for almost $1 billion rather than face the moderate court.
This waiting game is probably hurting the immediate conservative cause more than liberal, but with life-tenure at stake, Senate leaders are hoping to sway the future of Supreme Court precedent if a Republican president wins in November -- or at least force a moderate if the Democrats win.
While the Republican-led Senate is doing a disservice to their calling by not even holding confirmation hearings (they have the power to reject almost anyone they want to), this is still the separation of powers at it's finest, using the system to ensure your own platform and agenda.
While they probably should give the famous Bush-era 'up-or-down vote' to President Obama's nominations, the Senate is really highlighting the importance of the president's power to nominate SCOTUS vacancies in this election year, something all voters should be considering in each presidential election.