I was wondering 🤔

I was doing some research on IVF and PGS testing. Maybe you ladies know the answer. Why are egg retrieval’s done 36 hours after trigger? I’m asking because if they know the eggs are still going to be there then why do they do iui’s 24 hours after trigger? I mean maybe that’s why most fail? If you do the iui at 24 hours and ovulate at 36 hours the chance of washed sperm still around is very little. Plus the washed sperm can keep swimming. What happens if your retrieval is for 36 and you release the eggs before that? Can that happen with IVF? Sorry for rambling 🤫