> But I have already thousands of e-mails and text, how can I be sure that in 40-80 years there will be machines or programs that could read my old text files.
You actually have a much better probability of being able to at least view the contents of the text files on a machine 40-80 years in the future than if the same data was in some other format. I.e., try to find a way today to read an old WordStar, WordPerfect, or XYWrite file from the dos world. And those programs are not yet 40 years old... Yet a same age ASCII text file (assuming you migrated it off of floppies along the way) is still readable.
Assuming you can read the media, it's actually not hard to read old DOS word processing formats on modern PCs: both software and services exist to convert them, and, worst-case scenario, you can still run old DOS word processing software on modern PCs through virtualization and emulation.
Wang WPS files on open-reel tape, say, or Locoscript files on Amstrad 3" (not 3.5"!) floppies, are admittedly much harder to convert, but by no means impossible. Worst-case scenario, firms exist that'll convert things like this as a service.
You actually have a much better probability of being able to at least view the contents of the text files on a machine 40-80 years in the future than if the same data was in some other format. I.e., try to find a way today to read an old WordStar, WordPerfect, or XYWrite file from the dos world. And those programs are not yet 40 years old... Yet a same age ASCII text file (assuming you migrated it off of floppies along the way) is still readable.