our vet doesn't do all boosters every year. rabies is every 3 after the first puppy boosters and the 1st yr booster, and i think distemper is every 2 and lepto is every 1, though i could be mistaken. we also got Lyme boosters and a few others for our dogs, since lyme is a big concern where i live (my mom's dog has it) and we travel and go hiking and to dog parks often.
i've had dogs that received boosters into old age and never had any problems. i think (just like people) some dogs will have bad reactions, some won't. every dog is different!
I think giving boosters depends on the risk factors too.. our "outdoor" saint was more exposed to stray dogs/animals etc. than our inside dogs. our current dogs travel a lot and go to dog parks/etc., so it's important to us that they stay up to date on vaccines (city rules) or we could get a hefty fine, and we also can't get them licensed unless they are up to date on rabies and distemper.
personally, i don't think that boosters can be too harmful only because of the science involved... you're most likely just giving your dog a virus and the antibodies for it, and if he already still has those antibodies in his system, he'll be able to fight the virus either way. i think the big problem tends to be what else is included in those vaccines- ie preservatives and chemicals to make the body absorb things faster, and as far as I know there haven't been too many scientific studies done to ascertain what problems that could cause.
however, vaccines are made in different ways, and there are various forms of every vaccine and some are stronger than others and some are more risky than others. you should ask your vet what type of vaccine it is (some use a live virus + antibodies, some use a "fake virus" + antibodies, and some use a dead or slightly different virus +antibodies, and each type requires boosters at different times, since some last longer or are stronger than others). i think the ones using a live virus are the most effective, since it is literally the exact virus that your dog (or kid, you, etc.) could encounter in their daily life, but i think it has the highest risk because there's always a chance of getting the disease through the vaccine.
personally though, i think vets just want your money, and so do the pharmaceutical companies that make the drugs (which also can pay lawmakers to mandate vaccinations yearly, even if your dog may not necessarily need them). i think it's all about the money and not about health.
if i lived in a place that allowed a test for immunity to the viruses in place of the vaccine, i'd probably choose the test, unless it was significantly cheaper to just do the vaccine. i don't see the point in exposing my pups to unnecessary risks (there's always a risk with anything, including vaccines). i don't know that repeat boosters are a problem, but i don't think they are always necessary.
sorry, totally long-winded reply!