These attributions are not infallible, you know. The industrial revolution led to a huge increase in material prosperity, so there was a lot more stuff in print, which are the sources of these dates. People might very well have been using the word "cheeky" in speech in 1800, without it getting into a book the people at the OED could cite.
Certainly if Mr Darcy were having the same conversation about his library in 1850, he would have needed an income well over 10,000 pounds to spend on books. (That's why, in one of my stories, where the industrial revolution started earlier, and Mr Bennet built a very big house on top of Oakham Mount, he needed a more modern library. There weren't just shelves around the perimeter of the room.)
Certainly if Mr Darcy were having the same conversation about his library in 1850, he would have needed an income well over 10,000 pounds to spend on books. (That's why, in one of my stories, where the industrial revolution started earlier, and Mr Bennet built a very big house on top of Oakham Mount, he needed a more modern library. There weren't just shelves around the perimeter of the room.)