My wife and I talked about this, we've used trackers to increase our chances of conceiving and prior to that I had never really thought about how effective timi

My wife and I talked about this, we've used trackers to increase our chances of conceiving and prior to that I had never really thought about how effective timing could be. That said, if you absolutely need to not get pregnant, it's not useful. I would also never suggest this to my minor daughter. The best use case is for someone who would prefer to have like 5 kids over 20 years rather than 10 kids. I also think people really underestimate differences in fertility at different ages. An 18 year old is way more likely to get pregnant than a 35 year old. I'd bet if a 35 year old woman was reasonably careful with natural planning, she could avoid getting pregnant until menopause, but I think there's no chance that an 18 year old with average fertility could make it to 25 without having at least one pregnancy.