I buy both of ours Scalibor collars from the vet. They last 6 months and we haven't seen any fleas or ticks. I forget to put on the topicals, so I went to the collars.
BTW if your pet had fleas, you should treat your house. If there are eggs in your carpeting or furniture, you are looking at about a 6 week process. Sorry, but we went through that a couple of years ago and it sucks.