Items are, in back end, ordered by position (/lib/class.ListIt2ItemQuery.php,
line 254). For a short list of items that's OK, one can manually change the
order by clicking one of the columns. For a long list it would be convenient to
be able to set the default ordering field, e.g. expire date (end_time) in stead
of position.

Ordering by clicking a column only orders the items already displayed on that
page, not of all other pages together. For a long list it then is necessary to
display a (very) long list on one page or view several pages, reordering every
time.