I now find religion and its benefits useful as I begin to understand different concepts of the game. One thing is still not too clear though. Say I have a Great Prophet and want to use him to convert another civ's city to my religion. I figure converting his fringe cities will be a waste, as there is usually only a couple of population to convert. But if I send him deeper into their territory to a larger city and convert it, surely sooner or later the city would convert back due to pressure from the enemy's surrounding religion?