hrnmsf, you are totally correct, and I realized after reading your post that I need to clarify something in my earlier post.
I have realized that I don't necessarily look for surname matches as much as I have a 'running tab' in my head of names that appear in certain areas frequently, as neighbors, or as 'married into' names. Those names as as important as any surname. And you have to also be willing to consider how names varied in their spellings. I have Troublefields who were also Turbevilles and sometimes Turbyfills. Moores and Mores. Parrott and Perotts. Any combination thereof! And then there was the (as yet unsolved) Johnson also once listed as Butler. Go figure on that one.