Usually....mentioning or discussing or telling or listening to both your past experiences in your both previous relationship make us irritate and can always led to quarrel and may be worse....
Apparently it help the relationship more open and transparent..
Answer briefly:
1. Do you like hearing your gf/bf past relationship and ex's?
2. Do you tell your gf/bf your past relationship and ex's?
3. Should you both tell every details as to why, what, when, how your ex's?
4. what's the feeling of hearing it from her/him?or saying it?