@Phoenixflambe
Really, the only way to do that is to go with something that has lasted long enough that you trust it to survive, or to create your own domain.
But, either way, any content you post can be lost.
If it’s on your own server, you might have a hard drive failure, or the data center might get flooded or be destroyed in some other natural disaster.
Or maybe your ISP or host gets bought and the new company doesn’t like your content.
And if you host it on someplace that’s enormous and will be around forever - like LiveJournal or on a Yahoo Group - or even a Facebook group - then some day it will be gone and so will be your content, either because the company itself goes away, or the company changes it’s policies.
Everything shuts down. Even your own stuff.
So keep backups of your content, and backups of the backups.
And live with the situation that you have today - if you want something that’s going to be around for awhile, there’s lots of existing free hosts for almost all kinds of content. Most if not all of them will still be here in a year or two or ten.
Just make sure that you keep copies of what you want to save.