As a former history student who did post graduate studies, the converse is actually true. It's desirable to have that gap because you don't have that preconceived notion or aren't influenced by fresh events. It is that detachment from events that leads to more objective writing. And it is also true that as more archives are opened, commonly accepted notions should be re-examined. I'm not saying I agree with Combat on his interpretations, but his historical principles are sound. Excited utterances, etc. may be of probative value in a particular case but in an event such as World War II, where the contemporary writer is expressing what he knew but not necessarily having access to all the facts or information a leader may be making, it's not necessarily the authoritative word.