Heartguard all year round?

We only give heartworm prevention during mosquito season also. Some vets will have you test every two years if you do year round prevention, but will have you test every year if you only use the prevention seasonally. Our vet will only prescribe it if we test once a year no matter how often you use prevention, so we just do seasonally to save a few $$. (Just one of the reasons we are looking for a new vet)

I've heard the same thing.  About half of the vets that my friends go to say that you can use it only during season and you'll be fine.  They emphasize that it's a marketing strategy to make you use it year round.  My vet, and some others say that there professional opinion is to take it year round, and "why take a chance."  Let me know if you come to a conclusion about this.  My regimen will continue to be seasonally unless I hear something really convincing...it's expensive...and so far so good!

I use it all year round.  Sometimes spring (with the puddles and much warmer weather) arrives early - and suddenly.  Sometimes we have a much warmer than usual winter, even though we're having a lot of rain.  Last year the trumpet vine on my trellis was blooming in January and my impatiens lasted all winter. That's not the norm, but it does mean the skeeters are going to be around at times when they normally wouldn't. I  just don't want to be caught unprepared.

Joyce

Here in Iowa, Spring RARELY catches us unprepared! We're usually waiting for it with our flipflops in the closet next to the snowboots LOL! []

I used to only use Heartgard when the mosquitos were out ( frankly because it's cheaper and I didn't think it was needed). However, when we only gave that to her during the summer and were off in the winter, Cassidy developed roundworms which were kind of exspensive to treat. The Vet said the Heartgard would have prevented her from getting those. And since it would have been cheaper for me to keep on the Heartgard all year long, I've decided to give it to her all year long now. Our Vet recommends it year-long. Plus if we do that, we don't have to pay for the blood test at the next visit in the Spring.  Oh, and thanks for reminding me to give the dogs their Heartgard! It's the 1st! []

Heartguard tends to be less reliable -- and it ONLY works on heartworm microfilaria.  I use Interceptor because not only does it work on heartworm microfilaria, it also helps protect against other nasty parasites like whips and hooks. 
 
The problem is this -- ivermectin or milbemycin (Heartguard or Interceptor) only stay IN the body for 24 hours.  When they are called 'preventives' it only means they prevent the **maturation** of the heartworm microfilaria.  It doesn't prevent them from getting 'infected' in the first place.
 
If you give your last dose of heartworm 'preventive' on October 1, and your dog gets bitten by an infected mosquito on October 3rd -- that dog HAS BEEN infected.  And if you don't give preventive til the spring then you have to test, etc. -- AND if ... in that period ... the dog has gotten infected, you've given the heartworm like 6 months to mature and you may then have to go thru treatment with the dog.  THAT is tough on the dog. 
 
This is why they are advocating year round protection -- also, with the advent of fruit and veggies being SO transported all over the place, that load of bananas from Mexico may contain mosquitos that travel home in your groceries and so you get a stray mosquito that may bite your dog and THEN die. 
 
Using a product like Heartguard or Interceptor is minimally problematic -- it doesn't stay in the dog's system long term (Revolution, however, stays IN the bloodstream at least for that whole month) so the impact on the body is pretty minimal for the risk it reduces.  I use Interceptor and would do it year round no matter where I lived simply because of the reduced risk of other parasites. 
 
No one will hate you if you don't use it -- it's really all about how much 'risk' you are willing to take.  I give mine Interceptor and then give them milk thistle for 3-4 days afterward just to mitigate my own damages and help the body eject traces of anything that might remain and help the body cope with it.  But going THRU heartworm treatment is VERY VERY hard on the dog -- and frankly I'll do about anything to reduce the risk of that.

We use Interceptor year round except we do every 45 days instead of 30. I also give the Milk Thistle for a few days after the Interceptor.

I give the last dose of interceptor after we've had several hard frosts, and resume in the spring. The risk of being infected during the winter is almost nil.

Depends on the winter.  And doing it after "several hard frosts" is completely different than doing it by calendar.