I was reading on another dog forum that some vets are no longer using Frontline products because the ticks and fleas are becoming immune to the product. We have used Frontline Plus for years and it has always seemed to work well for us. We only use it for about six to eight months out of the year depending on the weather. So I was just wondering if anyone is having a problem with this product not working? I plan on asking the vet about it on the next visit. We also use Interceptor for heartworm all year round and last year our vet was telling us that the dogs should be tested every year because they are finding that the pills are not working as well as they did in the past. I am just wondering if it is really that the insects are becoming immune to the products or if it is a problem of owner compliance?