When I was a young mum in the 1980s, I used to donate my O Rh negative blood every 6 weeks in a process called plasmapheresis ( ??spelling).
Basically they would take a pint of my blood, separate the cells from the plasma, then return my red cells, so I didn't become anaemic.
A car from the Scottish Blood Transfusion Service would pick me up from my workplace ( I wasn't driving then) then take me home after the procedure.
I had given blood six monthly before that, "repaying" the many donated pints my brother had received before he died of leukaemia aged 12.
However, after I had the rubella vaccine when I started teaching, and also caught chicken pox, I developed antibodies which were very useful for treating sick babies. This was picked up from a regular donation, then I was invited to come 6 weekly. I did this until I was expecting DS2.
I didn't now that you could still donate in your 60s, I will look into that, happy to do it again.
I'm not sure if I've remembered all the details correctly, it was a long time ago. Maybe Ladystardust knows about this, but I was definitely a female donating plasma in the 70s/ early 80s.