In my experience it’s 100% effective over a couple longterm(ish) relationships that total to about 4 years in my early 30s. Average around 3 to 4 times a week after accounting for time apart. I guess I could be sterile in my older age?
I have five kids all five were conceived during a single act. Pulling out is the only form of birth control my partners and I have ever practised. in my opinion even for a very fertile person if you ( and I’m not sure how someone could fuck this up ) actually pull out there will be no conception.