you are right. i had a brain fart.I wouldn't correct this usually but OP seems to not know much about the topic and might get the wrong impression here, but it seems you've got the two donation types switched around. Plasma can usually be donated every couple of weeks but won't do much (anything?) to RBC really and whole blood is every 12 weeks here and will decrease RBC and iron in general. I've always given whole blood a few times a year altruistically and now I just see it as a little bonus when it comes to health preservation on gear.
I have heard that regular plasma donation does wonders for cholesterol but unfortunately the few times I've done it I've felt like I've been hit in the nuts every time the saline/RBC mix starts being infused back in. That kind of awful pit of your stomach discomfort.
the type of donation i have been doing is called 'double red cell' and the place i go only lets you donate every 6 months. its amazing and really knocks the shit out of my RBC and hematocrit and i feel great after.
they don't even do plasma donations but also offer whole blood which they let you do it every 2-3 months.
the cool thing about where i donate called oneblood.org is that they tell you like a week later where your blood went to.. what hospital or medical place. so i love that..