Gamer ADD?

So I've been working on developing a historical town for the beginning of an Early Modern Campaign setting. I was creating a town in Bohemia where the first events of what would turn into the 30 Year's War first started to brew. After a significant amount of research, I realized that many of my assumptions I had made at the beginning were just wrong. Essentially, I had 'wasted' my time and the town I was creating never existed.

So it got me thinking, why am I holding myself to a rigorous historical standard? So what if the town I made was not even close to what it was in 1618? I can still use what I have created and just drop the pretentiousness of a rigorous historical representation.

So I followed this line of thought and have been considering dropping the whole "earth" geography. I still want to create a D&D campaign based on the actual time period. Yet, I am still ambivalent.

So on one hand, I can either use real world geography and just rework it to my needs (Oh, there's no major town here? There is now!) or grab a supplement like Greyhawk or HarnWorld and just similarly rework it to my needs. Does it make much of a difference? In the micro-sense, it doesn't really make a difference. Only in the big picture, if the PCs care, is there a difference, such as, would you rather crusade for Pelor or the Counter-Reformation?

So I'm torn if I just don't want to go back to a fantasy setting that is already "spec'ed" out for use in an RPG or adapt history/earth to a fantasy game...

Or is this just gamer ADD and I need to stick to one course of action until completion?