We got a reminder in the mail today from the vet about buying new packs of heartworm pills for the winter. I've never given our dogs the pills in the winter -- just from June-November. It seems to me that it's better to take them off the pills for 6 months over the winter, so they don't build up an immunity to the medication in the pills. Also, is there really any point in giving them heartworm pills when the likelihood of them getting heartworm in the winter is really small?? I've had my husky for 12 years and she's been fine with the 6-months-on/6-months-off schedule.