Web pages are not forever
Writers like to think that their unique combination of words are meant for permanence, and serve as an eternal inspiration for future generations. This, combined with the lack of durability of written words on the Internet, stimulate initiatives for creating future safe web-archives.
We all like to think that we invent new ways of looking at the world, when we in reality are just re-stating or re-wording ideas that have already been presented before.
We are merely blending ideas. A thing you create that appear novel is often a minor change away from a thing that someone else created before you.
This is good. You should not be held back by the fact that someone else did almost the same thing before you. Go ahead, copy and re-mix!
Restating what we already know and adding your own twist is a great path to follow, if you want to come up with something new.
So, should you be worried that web pages with your ideas and thoughts are not going to available in a few years? — Certainly not!
Good ideas will be repeated, iterated, modified, restated, and re-distributed. They will survive, even when the original source is no longer available.
Your web-page may not be appropriately attributed, but your ideas can be permanent.