This is a very confusing feature, and I don't think the available help or even workflow dialogs explain well what is going on.
The short answer is you are better off also manually blocking the dates you will be on vacation so that you don't have any reservations staying during that period. You can also snooze during that period if you don't want any inquries while you are on vacation.
Let me try to explain this with an example.
It is December 2015 and you are going on vacation the first week of March 2016.
If you don't want any guests to stay at your place during your vacation, manually set the vacation dates to "blocked" (not available) in your calendar. This means that guests searching for your place will not be able to find it during your vacation and won't be able to book and stay there.
Now if you go and snooze your listing for the first week of March nothing will happen immediately. But on March 1 your listing will be snoozed. That means during the first week of March nobody will be able to see your listing for any point in the future. A traveler wanting to book your place for April 2016 will not be able to during the week it is snoozed, they won't even be able to see it. But if they search for it in December 2015 or any point before or after the snoozed week they will.
So really snooze just prevents you from getting an inquiry for the future that you might be slow to respond to. Like if you are on a cruise with no internet, and you care about your Superhost rankings like responsiveness, you might get an inquiry on the first day of your vacation and not respond for about a week, when previously you always respond on the same day.
One last way to try and make this concept make sense is I would suggest there is never an advantage to snooze dates in the future, you should snooze right when you are about to go on vacation. This will prevent confusion about future snoozes.