Spell Sponge

Your mystical connection with your spellcasting master attunes you to helpful magical effects.

Prerequisite: Animal companion or familiar, share spells ability.

Benefit: Whenever your master targets you with a harmless spell with a target of "you," the spell's duration is doubled as if modified by the Extend Spell metamagic feat. This does not affect spells with a duration of concentration, instantaneous, or permanent, or spells already modified by Extend Spell.

Source: Animal Archive