I have read lots of stuff about vaccinating, and basically I think it boils down to the fact that whilst some parts of the vaccine are probably long lasting, there are other dangerous and still very prevalent killer-diseases against which there are no long-term antidotes as yet, so the combined vaccines are still the safest option.
It would be good to have some statistics from someone other than a pharmaceutical company, although I have to say that at the Blue Cross our early puppy vaccinations have been altered to give more of a gap between vaccs because of recent findings.
It must be devastating to have a puppy die after vaccinating, just as with the current debate about MMR for children (although mine were done and thankfully had no ill-effects). The knee-jerk reaction is to not vaccinate, but there are still cases of Parvo virus (we had a local Vet needing isolation for an afflicted dog) which can be a killer ... could you rest if you thought you had left your dog vulnerable to that?