I do not use a (chemical) tick repellent and yep, I'm pulling ticks off my dogs -- well, not regularly, but not rarely, either.
Beau tested positive for Lyme this year, Rowley for Lyme in 2016, Dee for ehrlichia in 2016, and in the past, Miss Pip was positive for anaplasmosis one year.
Twenty-eight days of doxycycline has proved to be effective at wiping out all the tick-borne illnesses that my dogs had. I would rather not use the preventives -- that have a very uneven rate of success, from what I read -- when I know I will test annually and I will treat every positive with a month of doxy.
If heartworm were so easily treated, I wouldn't bother with preventive for that, either, but heartworm is a nasty customer and I never want to see a positive on that again, whereas I am resigned to my dogs periodically testing positive for TBD. As a vet tech in my BC rescue pointed out recently, it's almost impossible to keep your dog away from ticks, they are now everywhere in the Midwest.
Cedarcide makes TickShield, which is pretty effective, in my experience. If I remember to apply it to all my dogs, no matter how dense the coat may be, it does work. And it smells nice. https://www.cedarcide.com/ticks/