For dog owners Re: Heartguard. Do you discontinue use in the winter when there are no mosquitos then start back in the spring?

Our vet suggests we go all year with this. We are in the US Southwest with basically mild winters but I haven’t seen a mosquito since maybe October. Doesn’t mean they are not around but I’m not seeing any. He says all it takes is one that is a carrier to bite and we open up our dog to heart worms. Heart worm treatment is miserable for a dog and is always extremely expensive. Some dog’s don’t survive this treatment so I don’t want to take the chance.
There is the downside of this med as it is a pesticide you are putting in your dog and does have some effect on the immune system.
It would be good to know if there are alternative treatments for prevention that really work. Heart guard works for sure.