James Tanner in the Blog "Genealogy's Star" has written a great article on this subject. He uses his own search in Arizona as an example, but with very little effort you can get the idea and apply it to your own research.
The "limits" of our research essentially are defined by what you are looking for and what records exist for the time period in question. You might recall an earlier post on this Blog (20 March 2011 titled "A Date Guide to English Genealogy") that also talks to this approach...check it out.
James' article is apparently going to be in several parts, and this is the first. By the way, he references two helpful print resources, Red Book and The Handy Book for Genealogists which we have in our collection at the Genealogy Center.
You can read the post at http://goo.gl/4vDrH