Or wonder if you were accused of murder and they used luminol on your tub, would they think it's the murder scene? Or would that be the best place to hide evidence because they'll assume it's just because you're a girl...
As in seven years WORTH of blood (the amount of blood needed to live for seven years) or seven years BLEEDING (the total amount spent menstruating)? Your unit of measurement is confusing.
The amount of blood per period is on average 40ml (a relatively tiny amount). This is a lot less than men imagine based on the stories girls tell. Also most of it is clotted and does not run like normal blood. The average volume of blood in one human is 5000ml. It therefore takes 125 months to lose the amount of blood equivalent to one person, which equates to 10 and a half years. I think what windscryer is trying to say is that the duration of periods adds up in total over a lifetime to 7 years, although this can vary massively depending on the duration of your periods.
"Ah, yes. I was wondering what would break first. Your spirit, or your hymen!"