Hah. I'm a self employed freelancer, but a friend works for (MegaCorp Intl) and every time we go for beers he mentions that he has "Unlimited Paid Time Off". But whenever I ask if that means he could take a few months to hike the Andes with me, he says.... well, no, actually they'd fire him if he took too much time. How much is too much? I ask. Well basically anything that would make them notice his absence, apparently.
And there's a problem in the other direction too - I don't expect people who really can leave for a few months without their absence being noticable to have much job security.
Every company is different. I’ve had the “unlimited time off” company where the CEO would go after anyone who took a week or more.
I’ve also had the unlimited time off company where I took an actual month off and it was fine because I got my work done.