Writing outside one's time - how do you know what you don't know?

I recently attended a fairly successful production of Naomi Wallace's One Flea Spare.  I'm sure there will be some plot "spoilers" in this review, so stop now if that bothers you.

The title comes from a line in John Donne's The Flea, and seems a fairly apt title, given the mingling between the classes that occurs in the play.  Interestingly, this is one of Donne's less overtly religious poems/sonnets.  One thing that may be a bit misleading is that Donne is from an earlier era (1572-1631) than this play, which is set in 1665 (the Great Plague of London).  As I was looking up some material on this year, it turns out that the book that informed me the most about it (Defoe's Journal of the Plague Year) is actually a historical novel.  Defoe did live through the plague and the Great Fire of London, but was only about 7 at the time!  Who knew!?

Anyway, this simply reinforces that I don't have a very good handle on how people thought/acted in that era, but I am not sure Naomi Wallace does either.  (One of the more interesting debates is whether people had a fundamentally different view of what it meant to be an individual or whether they had an "interior life."  While I suspect this is somewhat overblown, there certainly was more collective behavior then.)  I would certainly have expected more references to God throughout, not just occasional asides.  Most of the interactions between the master and the sailor/servant really struck me as how we envision the Georgian Era heading into the Victorian Era and not how it would have been in 1665.  I was also somewhat doubtful that 1) Darcy Snelgrave would bother trying to save a horse from the fire (this strikes me as something more modern where we have elevated horses to the status of companions), 2) that she would possibly have survived her burns in that era, and 3) that had she survived, her husband would have turned away from her so completely (rather than assuming she had been granted God's grace). 

So it is an interesting experiment to try to write so far outside of one's own experiences and time, but it can be very hard to be convincing.  I did not wholy buy into Wallace's choices, but I still thought it was an interesting take on what life would have been like in that era filtered through the author's preconceptions and preoccupations.

Have you ever tried to write so far outside your own era, and did you think you succeeded?  Have you ever been "convinced" by another author tackling this task?