He asked what the limit was. "Unlimited", they replied. "Honestly?", he ventured. "Yes, unlimited".
"OK, then", he said, "I'd like to book the entire year off".
"Oh no, you can't do that!", they replied.
"I thought so. So what's the limit?", he asked again. "There is no limit", they replied. "But you just said I couldn't have a year off", he pointed out. "It has to be reasonable", they said.
This went back and forth. In the end "unlimited holiday" in the UK for this firm was 28 days. That is the statutory legal minimum in the UK. If he went over this, it would likely be accepted at the time, but "noticed" in performance/salary reviews, etc.
So, in short, unlimited vacation is a con, and you should try the above yourself. It'll lead to an interesting conversation, although it may harm your chances of getting an offer if you time it wrong.
[1] By US standards :) For instance 25 days plus ~10 national holidays.
Hopefully someone with first-hand experience or more knowledge will elaborate a bit on this.
Since you're responsible for getting your work done, you can take any manner of time off provided that the results hold up. This past year, I prolly tallied anywhere from 4-6 weeks off, technically speaking. Unplugged though, a handful of days at most. (Otherwise, mostly on vacay but maybe a few hrs worth of work a day sprinkled in morning / evening.)
Because I own my area of work + results though, during decent chunks of this time I still answer emails when I can, try to unblock people etc. So it means that I get to travel more and see other places, or work in other offices (would say 'remote' here but some are in places like NYC & Seattle so hardly remote in that sense of the word!)
Then, when I am around town in San Francisco, I make a point to check in with people in person, often through the evenings. And work part of the time on Sat/Sun to unblock people if I need to review or provide someone else the context to do so.
For my role I have made this work and love it, but this unlimited option is not for everyone. And there is a cap to how much you can realistically be away and still get things done.