Extend Spell

(Player's Handbook v.3.5, page 94, DnD 3.5)

[Metamagic]

You can cast spells that last longer than normal.

Benefit

An extended spell lasts twice as long as normal. A spell with a duration of concentration, instantaneous, or permanent is not affected by this feat. An extended spell uses up a spell slot one level higher than the spell's actual level.