The mage can, as well as assigning Duration with a spell factor, create a condition under which the spell ceases to function.
Doing so can increase the Duration of a spell, although the mage must still spend Mana and a Reach if Duration becomes indefinite.
The more improbable the condition, the smaller the bonus to Duration. Some mages use the Conditional Duration to levy curses designed to teach a target a lesson (“You will suffer boils on your hands until you dirty your hands helping another out of kindness.”), while others employ this Attainment tactically (“This floor will vanish the second I snap this glass rod.”).
Spend a point of Mana to add a Conditional Duration to a spell. Doing so adds factors to the spell’s Duration based on the nature of the condition.
An improbable condition (one that is unlikely to happen given current conditions) adds a level of Duration
An infrequent condition (one that will eventually happen, but does not happen often on its own) adds two levels of Duration
A common condition (one that will almost certainly happen in the near future) adds three levels of Duration.
When the condition is met, the spell ends regardless of how much Duration remains.