I think, with your rp writing if you try reading a novel or two, or if the period (like medieval Europe) doesn't have such things, some of the poetry, or tales and stories, of the period in question. Those give a better 'feel' of a given period where the people who lived then are concerned, and when combined with your researches, should help you get the tone of your pieces right on. I wouldn't worry overmuch about trying to get it too precise: after all, role playing games are supposed to be fun, not work!

For example: to get a feel for the world of 18th century England, one can't do better than to read any of Jane Austen's work; and then watch some of the modern screenplays adapted from her stuff. In the books, you get historical accuracy for the period, because that's when she lived and wrote them, and in the screenplays you'll see them adapted to modern usage, while still retaining the period's ambience.

Hope this helps you guys...