Kong gets his preventive heart worm chewable tablets once a month. For me it is one of those things, I'd much rather have him take it and not need it that not to take it and something happens, for me its just not worth the risk.
My boy gets heartguard and frontline year round. I wondered a year or two ago about stopping the heartguard through the winter months (northern Illinois) but came to learn, no - that is dangerous. No mosquitos during those months but the heartworm's life stages will keep right on developing regardless of outside temperatures. Its real important to continue the heartworm preventative year round.
We're in Virginia and both our dogs get Heartgard Plus year round in addition to Frontline Plus year round as well. We go hiking and camping a lot so ticks are a big problem for us. For instance... Today is February 4th and after bringing our dogs inside from a mini hike, I saw a very small baby tick crawling on our GSD that I got off. It is 60 degrees outside today and was like 20 degrees outside last night, darn ticks are resilient.
We only use Bravecto for fleas and ticks. Thankfully Heartworm is extremely rare where I live, I've worked at a vet clinic for 4 years and I have never seen a dog test positive for Heartworm. It really just depends where you live. I know in my county, there has not been a single case in over a decade so I don't bother with Heartworm prevention. However I do think it is a great idea to test your pets every year weather they are on prevention or not.