separating cats due to flea preventative?

I put Advantage II on my cats about an hour ago and I've been watching them carefully for a reaction and make sure they don't lick it off. I went to get some stuff out of the dryer and they were licking each other. I stopped them. Should I keep them separate tonight (or longer even)? What do you guys do?

I just make sure they do not lick each other when their neck is still wet. As soon as it has dried I let them be.

how do you know when it's dry?

When its dry the fur will look normal again. It will look a little greasy but it wont stick up and look a mess. It only takes about 6 hours for it to dry. I would separate them, I know when my cat licks off PetArmor his mouth fills up with saliva and he drools everywhere.