Parasites are in the environment and mine run free so I usually worm after we've had a hard freeze, once a year for adults.
I worm a bitch right after she has bred.
I prefer Panacure for round worms, and I use Interceptor plus for heart worms all year.
If you do get tapes you'll see them in the stool, tests at my vet are more expensive than treatment and I check stools regularly anyway.
Young dogs are checked after being wormed at six weeks, at six month intervals until two years.