Invention of minor temporal stasis allowed conjurers to perform some quite interesting tricks during the battle. However, if the battle rages for long enough, minor temporal stasis will dissipate and all carefully prepared planning will become just a waste of time. For such situations, it became obvious that temporal stasis with longer duration is needed. Such spell is not exactly required at this level yet, but it is just matter of time when it will become necessary, so why not learn it now if it turned out to be not so difficult to master?

See also: break temporal stasis