What are marriage vacations called?

They are called trial separations. The spouses part ways but without plans to divorce. The idea is that the two people are supposed to think about the marriage and try to decide if they can save it.

When couples cannot get along, sometimes they find a short break from each other gives them some breathing room and a chance to do some serious thinking, which can be difficult if a marriage is full of tension.

On the other hand, some professionals believe that leaving a marriage, even for a short period, is just an excuse to leave it forever, and that most couples who separate on this trial basis eventually falter and head for divorce. Separations, voluntary or involuntary, add stress to a marriage.
Moreover, when one spouse wants a vacation from the other, trust, which is so essential to marriage, becomes strained.