Great topic! I will have to try and remember to keep an eye on this post for the feedback and thoughts and opinions.
I, like you, struggle with this too at times. I have no choice living in the USA but to vaccinate for rabies every 3 years, which I will do reluctantly. As far as optional vaccines, ie: Lymes, Lepto and Bordetella, I will not and did not do. The core vaccine like Susan mentioned. I did the puppy series and the one year booster. I have not crossed the bridge of having to make a decision on how often, if at all, I will do those past that point. Right now my thought is that the "4 in 1" is optional because it is not the law here in my state and after getting the puppy series and one year booster with that vaccine, testing and studies show those vaccines levels are still high enough for full immunity 5-7 years later. So I will most likely refuse that vaccine from here on out also and maybe do a titer test when we reach the 5-7 years mark and decide from there.
A little off your topic but I thought it was also worth mentioning: I also refuse to give mine heartworm meds or artificial chemical flea/tick treatment monthly. I am not going to give mine insecticides and pesticides on a regular basis as a preventive for something they do not currently have. However, I do have them tested for Heartworm and Lymes twice a year. I use an all natural plant oil spray, as needed on them when I know I am putting them at higher risk somewhere outside for fleas, ticks or mosquitoes. In the summer I also spray our yard with an organic natural "bug" spray every month that also is made up of plant oils.