[jonahrd]

There's an interesting dichotomy:

As a single user, you must assume that anything you upload to the Internet will be there forever, because anyone can download a copy and maintain it. This means users need to be careful about privacy-sensitive information, controversial opinions, etc.

But on a broader level we don't actually dedicate much effort at all to maintaining the bulk of what's posted online, meaning most important things will eventually be deleted.

[bombcar]

Or to put it another way - the longevity of something on the Internet is the inverse of what you’d want it to be.

[HenryBemis]

I'd phrase it like this - the longevity of something on the internet is correlated with its need/usefulness.

If someone needs that 'thing', they will download & keep a local copy, and then when if it disappears, then someone will ask for it on Reddit and voila! you shall provide.