The great thing about Simparica is that your dog is covered for an extra 4-5 days if you are a few days late with your monthly treatment date. Simparica has continuous killing activity for 35 days so it keeps going strong between doses, unlike some of the other products available. This extra coverage keeps the dog protected for the 4 out of 5 owners who admit to giving the treatment late. See how it compares against other popular treatments in our competitor section.