I wouldn't wait because it becomes very uncomfortable for them and harder for the vet to empty them. Logan hates to be touched on her thighs under her tail. She's shedding terribly in clumps there and won't let me brush her out. Hates her feetsies touched too. But LOVES her rump massaged. She'll turn around and practically put it in your face for a rubdown! Yeah, they're all different. Sensitive to different spots like people.