When does the Oath of Vengeance paladin's Powerful Justice ability expire?

Question

The Oath of Vengeance paladin's Powerful Justice replaces the paladin's normal Aura of Justice:

Powerful Justice (Su)

At 11th level, an oathbound paladin may spends one use of her smite evil ability to grant her allies within 10 feet the ability to smite evil, except they only gain the paladin’s bonus to damage, not her smite’s attack bonus or ability to bypass DR.

This ability replaces aura of justice.

Once Powerful Justice is used, how long can the paladin's party members "hold onto" the ability to smite evil? Must it be used in the round immediately after Powerful Justice is activated, or can the allies wait until hours later before activating their smite?

Once the ally uses smite evil, it lasts as long as a normal smite evil would, rather than capping at a minute like Aura of Justice (see e.g. Paladin of Vengeance: Powerful Justice?). I'm not asking how long the smite lasts once it's activated, I'm asking how long a party member can wait before activating their smite.

Answer 1

Until the individual ally's next rest

The allies are subject to the rules of Smite Evil (p.61, Core Rulebook), which state that

The smite evil effect remains until the target of the smite is dead or the next time the paladin rests and regains her uses of this ability.

This implies that the smite evil ability can only last until the next rest, at which point all uses (whether used or not) are regained. For the case of the allies, this is "regained" to 0.