Jackson had probably 10-15 ticks last summer. He was on Frontline but it didn't seem to matter. We switched to K9 Advantix and haven't got any, except one a few days ago (we were late on the Advantix tho... oops!) He tested positive for Lymes back in late December when he began limping and holding his back hind leg. I'm sure it was a tick from the beginning of last summer that he got, the vet said it can take months to show up. He got put on a 30 day antibiotic and he's good now.
Maryland is really tick infested.