
Having had dogs for 20 years we have only used spot on's when necessary e.g. dogs have traveled and the treatment is needed in order to cross borders or we have had "a scare" =dog in training club found with fleas.
We have never had a problem with fleas in the 20 years and our dogs go to training, shows etc where they meet other dogs and could pick up fleas.
Neither have we had a problem when they have had the treatment (apart minor skin irritation).
With a youngster we follow the normal worming routine but after that, our dogs get done every 6 months or so.
Unless there is a reason for us to believe they might have worms(eaten things, raw fish etc) and I will then just worm them just in case.