Why sweat Ginsburg. Kennedy and Scalia are 78 although I doubt they will retire under any circumstance unless they die or a republican is president.
You fear a Ginsburg death/retirement and a conservative nomination under a republican president and yet if the D's get the senate, they wont let a conservative walk away with it and vice versa if Hillary has to replace Ginsberg under a R senate. Tough option either way. Nor will a R senate let Kennedy and Scalia be replace by a liberal and vice versa with a R pres and D senate.
Best case is a D Pres and D Senate with Ginsberg retirement. Kennedy and Scalia aint going anywhere under a president hillary.
If there's a protracted Supreme Court vacancy, my best guess is that the voting public will end-up siding against the Senate. So if the President nominates #1 and gets rejected, #2 and gets rejected, #3 and rejected, and so on.. I'd be willing to bet that the President wins that public relations fight, especially after multiple rejections.
I also don't have much confidence that the Dems will keep the Senate after the 2018 elections. With lots of 2012-elected Dem senators facing a conservative midterm turnout crowd, hopes of defending a narrow majority aren't very strong.
Basically, I'd rather be the one nominating rather than playing defense.
(And you're absolutely right on Scalia & Kennedy.. as with Ginsburg, and as distasteful as this will sound, it's a game of waiting for Death to step-in.)