I'm not doctor or biologist or so, but I just thought so because of out own experience, see I had an ex girlfriend who cheated on me, met few years later a black guy who became my friend and he told me of his conquests, which among was my ex girlfriend, so I asked him all details and he could describe me everything even how her room looked like. Which led to my believe why she round that same peroid became harder to please, before she fitted like a glove to me and sex was fun, but then one day I saw a strange motorcycle on her place and she told me it was her friends, also her dad was cussing about killing a black guy that been on his domain, but i was to trusting back then, also that week i didn't had sex with her, it was a week later I had back sex with her and it just didn't feel anymore like before, she was more open and I had trouble to even cum inside her, let stand make her cum, so it led to me buying a vibrator to please her. And the only days he had sex was Thursday and Sunday of the week I had no sex with her and weekend after I had sex with her. So i'm not sure if every pussy is that elastic, but then again I have else no explenation why before she felt good and after he did that she no longer felt good anymore.