I've been thinking about this quite a lot recently as I've been trying to dig up information about 90's era dial-up bulletin board systems. It was a scene I was deeply immersed in at the time (or at least, one specific niche within it) and there is surprisingly little information left which is easy to find now, 30 years later. I remember the web being awash in more contemporary technical minutia than I could read in a lifetime. Now, the vast majority of it seems to be flat-out missing or at least very well hidden/distributed.
I think it is more accurate to say, "everything you put on out on the Internet _might_ never go away." Because my experience has been, a lot already has.