It can take anywhere from several days to up to 2 months for a warble to come out of a cat after the application of petroleum jelly or bacon grease. The exact timeline depends on various factors, such as the size of the larva, its location, and the cat's immune response. If you suspect your cat has a warble, it is best to consult with a veterinarian who can assess the situation and provide guidance on the best course of action.