Not for 12 hours at a time. Take a look at the addiction forums, it's a problem like never before. Have you not seen the study showing the refractory period is eliminated when presented with new mates? Kids before didn't have an unlimited stream of hardcore pornographic videos at their fingertips 24/7.
AFAIK the refractory period thing has never been shown to work with p**rn, only with real women.
(And I would wager that the phenomenon might hold up for a couple of additional real women. That's not the same thing as cumming dozens of times for dozens of hours. Your semen supply is not that big and your production is not that fast. The extra women aren't giving you more total c*m, they are giving you the ability to empty your stored supply faster.)
It was completely normal for teenage boys to jack off for hours at a time before the internet. I know, I was there, and so were my friends. Eventually you've got no semen to shoot even if you can keep an erection. Eventually the erection gets more difficult to keep and your skin just hurts from too much rubbing. All this is perfectly achievable with a few old playboy mags. If you don't have p**rn you still have potent memories of the hot girl in your math class the day before. At that age you can get horny looking at a hole in the wall.
The internet just provides a bigger stack of Playboy mags. It doesn't change the fundamentals of any of it.
The "problem like never before" is that some kids spend more hours of the day looking at p**rn. It doesn't raise the biological limits of what their bodies can do.
TLDR - teenage kids were horny before the internet.