Oh my, I was just about to post this same thing! I have always been a heavy bleeder. No cramps, no pain, but very heavy. After my DD was born, I skipped my period for a year while breast feeding. But when it came back, it was even heavier. Like you describe OP: "several big bright red clots(somtimes so large I wondered if I should be worried)" I am also over 35. And also heaviest on days 2 and 3. TMI: On these days I have to wear a big nighttime pad during the day and change as often as every 2 hours or my jeans/pants will get leaked on. At night I wear 2 nighttime pads, plus a towel over the sheets, because I will always soak through, a lot. Is this abnormal? I don't know.
I have two children, both conceived by merely looking at my husband in the wrong direction, both very large (4.5 kilo, 4.3 kilo), and have very large placenta (900g - average is I think 525g). Not sure if this is related, or just coincidence.
Being born puts you at a greater risk of dying later in life.