Extend Spell (Feat)

convert to a magic item for the rings slot, possible name 'Ring of Everlasting Arcana'

You can make your spells last twice as long.

Prerequisites: Caster Level 1

Benefit: An extended spell lasts one time category longer. A spell with a duration of concentration, instantaneous, or permanent is not affected by this feat. A spell with a duration of the current encounter now lasts until the next encounter. (Note that such spells often have little noticeable effect out of combat.) A spell that normally lasts until the next encounter now lasts until you take a full rest. A spell that normally lasts a full day (until your next rest) now lasts an entire month, until the next Moon. A spell that already lasted until the next Moon now lasts a year and a day. If the duration was already a year and a day, the duration becomes one decade and a day. This effect can only be applied once per spell.

Level Increase: +1 (An extended spell uses up a spell slot one level higher than the spell's actual level.)