The further back you go in your research, the more difficult it becomes. That's the genealogical rule, and it's demonstrably true. However, there are still reasons to be cheerful if you're trying to trace your family back to the 1600s.
By the start of the 17th century the established practice of keeping parish records had been bolstered by the requirement to send a second copy to the bishop - meaning genealogists have two places where