...is there a long lasting home made flea/tick spray for small dogs?

Its more than your dog. You have to clear the area where the dog lives. A main source for fleas is birds. Get rid of the bird bath.

most topicals or tablets are good for month, maybe 6 weeks at a stretch.

The Seresto collar however is advertised to last 8 months. Don't know whether that is true, but even it it is good for 6 months, that is longer than a topical.

Home made? no. Why home made? you can go to a vet or pharmacy and buy effective flea/.tick prevention spot on treatment. Supermarkt and pet shop stuff is useless and they are not licenced to sell insecticides that work. I'm guessing you want home made stuff because you won't pay the price for real stuff. Pets cost money... if you're not prepared to spend it, don't get pets

a collar yes,, spray no