Some spells are marked 'Remains in Play'. Such spells stay in effect indefinitely when cast. They only come to an end when the caster is slain, chooses to end the spell (which they can do at the start of any sub-phase) or leaves the battlefield. The casting Wizard can continue to cast other spells (but not the same Remains in Play spell) as it requires only a little concentration to keep a Remains in Play spell going.