I doubt that there is much more to the shift in the spelling of the Langstroth/Longstreth/Longstroth/Longstreath name than pronunciation conventions and historical move towards standardized spelling that paralleled the early migrations of the Ameraican Longstreths. The immigrants to America that became predominantly Longstreth arrived about 1700; the wave that used the Langstroth spelling after arriving in North America arrived 50-75 years later, so spent at least 2-3 more generations in the English homelands. In that interval, the US public school system had begun to develop, and towards the end of that time span Noah Webster's Speller had appeared and begun to be used in American schools. This educational tool tended to produce standardized spelling, whereas previously the spelling in many documents appeared to driven more by phonetics than tradition. This is true even in the early US census records where there are numerous spelling variations of the Longstreth name. There are even cases where the same newspaper spelled the name of the same Longstreth person multiple ways.
So the first wave of Langstroths to America had multiple generations to Americanize before their Langstroth cousins in the second wave came over, and the environmental pressures leading to accent, pronunciation and spelling changes were substantially different. I suspect also that in England, there was a similar movement towards standardizing spelling, in which case the second wave of Langstroths may well have "known" how to spell their name before they arrived, which might not have been the case 50-100 years earlier.
A small group of Longstreths in western PA adopted the spelling Longstreath, which is not a huge surprise if one recognizes that a diphthong accent is not particularly unusual in that Pennsylvania and West Virginia area. The peculiar thing about this particular spelling variant is that not everyone in a family necessarily adheres to it - so various sons and daughters of a father who uses the "ea" spelling, may keep the "ea" spelling, or may revert back to the "e" spelling. That makes for an interesting challenge for the genealogist to place family members, even now. The "ea" spelling currently has 3 geographical foci because of assorted migrations that have occurred - western Pennsylvania, western Ohio and Oklahoma.
The Longstroth spelling appears to be associated with a third wave of immigration from England. As near as I can tell, the original Longstroths may have immigrated to America from England to join the Mormon movement. They originally settled in Utah, but are now located in a few other western states also.
I suspect that there are more Longstreth/Langstroths in England than most people realize. A look through Facebook can identify at least 3 sets of families in England with members in the younger generations. And I encountered two or three groups without trying too hard in the Skipton and Yorkshire areas back in 2002 when I visited. There also appears to be a branch of the family name in Ireland. But I have not been trying to follow all these so cannot personally identify the assorted connects, even if I suspect they exist.
