Flea / tick products for dogs

Question
There are a few of these products on the market, some only available through vets, that are a liquid that is applied once a month on the back of the dog's neck.  Most are pretty expensive.  Hartz has a similiar product available in retail stores that is much cheaper.  Is the Hartz product just an ineffective "knockoff," or the equivalent to the others just at a lower price?

Also, I've heard that Golden Retrievers (I have one) are susceptible to cancer.  Should I be giving her antioxidant supplements as a preventative.  Mine is about 6 years old.

Thanks.

Answer
I tried the Hartz stuff once and didn't have good luck.  Our home is poor flea habitat.  As long as we only had one healthy young dog in the house, we got away without doing anything for years.  Then we took unprotected Gretchen to visit my sister and her flea bitten cats.  By the time we got home we had a mess.  Using the Hartz stuff and OTC flea spray we tried to clean her up.  I am not sure we had the problem solved before she went away to school or not.  

It is quite possible you would do better if you applied the cream before you had a problem.  Fleas are much easier to prevent than clean up.  I read a lot of stuff knocking all the OTC stuff.  I think some of it comes from those deeply committed to the idea that if it is more expensive, it must be better.  Plus, all the vets claim their stuff is better.  I guess if you have had flea problems in the past, you could try it.  There are various home remedies too.  I have no faith in them.  Many people claim they keep their dogs flea free, but then doing nothing worked for me for years.  

Since Aster came back to live with us 4 years ago, I have used Revolution on both dogs.  Aster has a flea allergy from back before all the good stuff was in common use.  I do think the Hartz stuff protected her on visits to Gretchen that summer.  It made a mess of her coat, so later I went with the Revolution.