Thing is also - I know this will sound trite and it isn't meant to - but you only need one of those good eggs after 35 or 40 or whenever.
I genuinely thought - after DS1 at 30, and 5 years later no DS2 - that we were secondarily infertile. We were almost at the stage of paying for IVF as you can't get any NHS treatment if you already have a child. Turned out in the end we were trying too hard (being tired and busy and overthinking and all) and going for, ahem, a magic bullet approach instead of the, ahem, machine gun approach we had used in the days when we had time to have lots of sex. And more to the point the 'aim' was wrong as it turned out I ovulated much earlier than I realised.
I don't say this to undermine the awful struggle and sometimes failure many women over 35 have in trying to get pregnant but just that as well as for many 'trying' and failing there are many (more? I dunno?) trying and eventually succeeding.
In the circumstance - almost all possible testing, prodding, poking, timetabling, mucus monitoring and ending up convinced DS2 was an absolute bonus, DS3 - conceived at 40 - was an absolute shock surprise
Now I'm not being thick, or light, or even smug, as I do know, with many friends in the position of it just not happening, that we clearly were fertile enough and that just isn't going to be the case for everyone.
But wanted to make the point that the 'cliff face' of fertility is an aggregate figure too, not to be applied to everyone in all circs. And amongst that figure, there are many many women hoping for a, or another, baby for whom it will happen.
The cost perhaps though is that you have to add 'eventually' to that sentence and that means, for my sister, for friends, at the cost of many lost babies and some prodding and a lot of distress and devastation.