Well I guess I’ve sort of studied it a lot the last decade. I was married to an older man for over 10 years, he was shocked to learn that his sperm was low in his mid forties, but we were told that was normal. We tried and failed to have kids for about 8 years. My marriage ended with him for reasons that has nothing to do with his fertility. After that I decided I definitely wanted kids, and decided to have them by myself. I ended up using frozen sperm from a bank, which requires I really look into my own fertility as well as the prospective fertility of the various donates. Frozen sperm is less potent than fresh sperm, and I had to become obsessed with figuring out my ovulation window through various techniques. I tried several times with different donors, but it only worked when I got a young sonar in his early twenties. Since then I’ve sort of been obsessed with fertility, male and female. I forget where I’ve read everything-so please feel free to do your own research. It’s kind of a myth that men stay fertile forever while women have a specific expiration date. Both male and female fertility goes down with age. But it’s a bit more noticeable in women. So I don’t really have any sources for you, but in my own fertility journey and research.