Once upon a time, and yet, only the once.

In an Annamite saga a certain king wished to build a town on a site he had fixed upon. All at once a tree bearing an unknown foliage and strange flowers sprang up on the spot. It was determined to offer these flowers to the king; and sentinels were placed to see that no one plucked the blossoms. A rock still pointed out in the north of Annam was the home of a race of genii. A young and lovely maiden belonging to that race visited the tree, and was unlucky enough to touch one of the flowers and to cause it to drop. She was at once seized by the guards, but was released at the intercession of a certain mandarin. The mandarin's heart was susceptible: he fell in love with her, and, pursuing her, he was admitted into the abodes of the Immortals and received by the maiden of his dreams. His happiness continued until the day when it was his lady's turn to be in attendance on the queen of the Immortals. Ere she left him she warned him against opening the back door of the palace where they dwelt, otherwise he would be compelled to return home, and his present abode would be forbidden to him from that moment. He disobeyed her. On opening the door he beheld once more the outside world, and his family came to his remembrance. The Immortals who were within earshot drove him out, and forbade him to return. He thought he had only been there a few days, but he could no longer find his relatives. No one knew the name he asked for. At last an old man said: “There existed once, under the reign of I do not now remember what sovereign, an old mandarin of the name, but you would have some difficulty in finding him, for he has been dead three or four hundred years.” --Edwin Sidney Hartland

Time in the SmallPowers multiverse is a complex thing.
  As in seen all the great tales of yore, time does not pass the same from realm to realm. Who, other than some rather mad wizards of the Order, knows exactly what currents drive each universe's passage from beginning to end. In our universe, the question is equally difficult to ascertain. Many scientists and philosophers have found their assumptions and explorations incomplete. It has led to many proposing that time, and by that space, is infinite. An explanation that does not quite ring true to the mind. However, there are many things in universes that seem less than satisfactory to our minds. There are whole branches of mathematics and science that strike one as being nearly magical in their obtuseness and unfathomable complexities. Once grasping them, returning becomes much like the door of the immortals in the tale above.
  For the wizards of the Order there is but one concern, and that being the existence of a universe. The end of the world, and thereby the end of a universe, is the fate they wish to avert. Manufactured infinity in a sense. Perhaps that is why magicians in many culture's iconography are branded by the mark of infinity. The wizards of the Order might not get such, as they seek it and know every well that too many places are doomed to have nothing like it. Unless they can get there before the end, find a victory, and then slip off to seek the next place that is threatened by non-existence. Each story in the SmallPowers saga is a glimpse of what that takes, what it costs to them in mind and body, and what kind of person would be motivated to strive for infinity for everyone other than themselves. The price taken by fate and destiny for spoiling their plans is beyond infinite.