After making the split, you only need to wait about 3 hours (Although 24 hours is advised.) Bees know within 3 hours that they are without a queen as the pheromone levels quickly are lowering.
Just because they have queen cells does not mean they will kill off an introduced queen. But to keep any possible damage to your new queen, if in fact one hatches (Bees are keen on hiding their own queen cells away from the queen) it is best to destroy any queen cells.
I never wait more than 2-3 days to release the queen. Either they take her in this time, or they don't. I hear some suggest up to a week. What a waste of production time being overly cautious.
Next time, make your split, wait till the next morning to introduce the queen, and she should be laying a few days later.