You can triple the duration of a spell.

Prerequisites: Extend Spell.

Benefit(s): When you cast a spell augmented with Extend Spell, it lasts three times as long as normal.Aspell with a duration of concentration, instantaneous, or permanent is not affected by this feat.

Alternatively, you may expend a use of mythic power to cast a spell as an extended spell (gaining only the normal benefits of an extended spell, rather than the increased benefits outlined above) without preparing it as extended in advance, taking extra casting time, or increasing the level of spell slot it uses.

Normal: An extended spell lasts twice as long as normal.