Lol, I really love these types of threads. Thank you, BC!
While I agree with most of Jbrix's points, I reckon a very important point he missed is the "time of the month" you fuck her, because it affects the temperature and (I can't prove this scientifically) the viscosity of her juice.
The best time to see her is right after her menses. The worst time is in the middle of her 4 weeks cycle, because that is when they are fertile, the temperature in her vagina is lowest to keep the ovum alive, and I find the juice is too "liquid" to feel anything. She just feels looser at that time of the month.