My Girlfriend Said Her Previous Guy Was Stronger In Bed

Guys, i was just having a conversation with my girlfriend/ wife to be about likes and likes-not in bed, and while listing her likes, she went on a story telling episode about her previous guy. The part of the story that caught my attention was when she said that her ex will do her for hours without resting. She said there was a time she visited the guy and he effd her from 12 noon to 5pm, that she could barely walk that day and was feeling so satisfied and fulfilled. She then said with all the fuss i was making about effing her out of her senses, that i came short of satisfaction, and that the guy was stronger in bed. You could imaging how furious and boiling i was feeling inside while hearing this from her in a normal conversation.

The facts are though that when ever we have sex, i am absolutely sure i last for atleast 15 minutes or more no doubt, my joystick is 5.7 to 6 inches erect and hard as wood, i do pre-intimacy and such, so what the hell is the problem? Is it even my damn problem or her's? I know for damn sure no normal guy will last for more than 20 minutes of constant thrusting. If she has to be effd for hours in order to feel satisfied, isn't she the one with the problem? On the one hand, i feel like i shouldn't even worry myself since she is aperantly the nimphomeniac not me. On the other hand, i feel that her "accidental revelation" is a sign of what's to come, as in she might be a cheater when married because of her insatiable appetied for marathon sex.
what's your opinion guys