Blake,
I worm pups once a week starting when they turn 2-3 weeks and slow it down after about 10 weeks of age, and grown dogs... I watch their stool and worm about every 3 to 6 months if all looks good or when the stool looks watery. But runny stools can be from over feeding or a change of food. My dogs are on concrete so re-infestation is low compared to dogs on ground floors.
Thanks Rueben. I guess I am ok then, as mine are also on concrete and I watch them pretty closely. I do give the heartworm pill on the 1st of every month too