3 quotes per paragraph is perfectly fine, ive gotten multiple 17s/18s with 9 quotes per essay and I know people who have got 20 with 9 and my school marks quite harsh. It really depends on how good your analysis is, and how well the quotes link to the question / your key arguments. Quantity does not equal quality and even then with 5 quotes per paragraph I struggle to see how you finish an essay. I can do 1100-1300 word essays in 45/50m and thats just enough time (for me with deep analysis and links to the q) to get 9 quotes. But then again its different for everyone.