I'm in the UK. 28 days of paid vacation time is the legal minimum (22 vacation days, plus 6 bank holidays). I get quite a lot more. Some places around the world have higher legal minimums. People in Brazil all get at least 30 days.
And people's plans are already made for whatever days they get, so unless there's a sudden influx of vacations, more trips just won't happen. That is of course expecting people can also afford extra trips, the locations themselves often being quite expensive.
And people's plans are already made for whatever days they get...
Maybe I'm unusual but I rarely have any plans further than a couple of months ahead. Whether I'll be going on any long trips in the next 12 months isn't something I have any idea about yet. It depends on loads of factors (money, weather, work, whether I can pick up a bargain, etc.)
Going anywhere where EV couldn't reach would most often require some sort of reservations; hotels, skiing resorts, museums, sight seeing etc all require some sort of planning if you don't want to absolutely burn money buying things ad-hoc, which would go counter the point of saving money with an ICE anyway.
A month or two in advance is just fine, most people can do as much. They do know how many days of vacation they get though, and it's unlikely to change, so any plan you have you keep.
