Code on the Road: Two Weeks Vacation is only a Recommendation, not a Rule
expatsoftware.com
expatsoftware.com
The trick is to be willing (as the OP points out) to carry out the bluff. This generalizes to all negotiating. You have to be willing to walk away, and the other party has to know you actually will walk away, before you get a deal.
In about 15 days I am taking seven months off to work on a startup + half a dozen smaller ideas. I talked to my boss about it six weeks ago, and he came by the other day to "make sure I wanted to come back in January." If that doesn't turn out (my startup takes off or they don't have a spot open by then), it's ok because I can always find another job elsewhere.
There are tons of great intensive Spanish programs both in Spain and Latin America that are cheap (mine was $3000 for four months, including an apartment and 20 hours of class a week). I have maybe eight months total of language education and I already speak better than people I know in their senior year of a Spanish major.
I remember being really pissed.
And then the VP of Engineering came to the rescue and said "I don't think you understand. He's going. The only thing you're doing is helping him decide to come back."