
Even if you think that a lot of session would make it cave then consider one girl having sex with 100 people 100 times versus another with one guy, but 500 times ,then? Who would make bigger cave? Also, for even skilled guy, it is not as easy to fuck hard during first time with a particular girl as is is later with the same girl. So we can conclude that rather girls with high body count will have smaller possibility of having cave, according to your logic.