It's incredibly beneficial to your pets health to have routine annual blood work done and heartworm season offers great discounts to help with this. (mcleanvet.com)
Puppies greater than 8 weeks of age should be started on preventative if born during heartworm season (May through November). (northcountryvet.com)
If you find you have skipped several months of heartworm prevention in the middle of heartworm season, you might do better to restart an ivermectin - based product rather than a milbemycin - based product. (vin.com)