I find around 36 hours is the sweet spot though you could go longer if you keep it bubbling. 24 hours is long enough for much of the sucrose to be consumed which will increase bacteria populations. If they are well fed they will begin fucking and multiply exponentially; then they will fight for dominance. The "bad" or anaerobic bacteria will slowly lose to the superior aerated bacteria. Average lifespan of bacteria is only 24-48 hours so after 36 hours brewing your tea should be at the height of activity; a good time to apply it to the soil. If you need to brew a tea longer than 36 hrs just add in some more compost to keep the party rocking.