Ooh, good thread. Always save everything you like; modern world is data and it doesn't look it is going to change, therefore you never know which assembly of bits and bytes might become a treasure at some point of your life. Anyway...
what do you archive?
Video game installers, movies, music and my save games are the biggest chunks of my archive, but it doesn't really end there.
I also have some comic books saved, some regular books, some wrestling vids, some dance videos from YouTube, some artwork, useful software and so on...
Most importantly for me, of course, is to save the things that I scanned myself and/or obtained from very exclusive sources (I always strive to make those public, but sometimes part of the deal is not to do so).
In particular, there are some vinyl discs and CDs which I could not find online and therefore had to buy and make digital myself. There are some movies I translated on my language myself. There is at least one movie, which I digitalized from VHS itself. There are some books I scanned personally. And then there's this particular paper from 1970's about Ancient Egypt which some american dude generously took from the library and scanned for me - all for free...
All this data is very precious, one way for another. While I do upload stuff wherever I can - Internet Archive, libgen, YouTube, torrents - local backup is still the most trusted storage of the bunch.
where do you archive / what do you use?
External HDDs. The most reliable storage aside from magnetic tapes, IMO. Every backup HDD has a backup of its own - so all my HDDs come in pairs. The moment any of them will give way to age, I will replace it with a new disc, using the other backup drive. Chances of two HDDs getting bad at the same time are rather low, and even if it will happen, chances that bad sectors will damage the same file on both HDDs are almost non-existant, so even in the worst case I will likely be able to restore all the data using two HDDs.
do you have a schedule?
Every 5 years all HDDs are formatted and rewritten in order to prevent them from demagnetizing.
have you ever lost your files and was saved by your back-up?
I lost? Not really. I do, however, have several old video game repacks that has since been gone from the web... for just one example. I didn't lose them, but those were lost nonetheless.
Plus, my massive backup have been very useful when I need to just fetch a movie to show or music to share or something else, whatever. I do not need to be afraid that files are removed or moved somewhere - I always know where they are and can execute/send things instantly.
For example, just now I've been recording another video from my YouTube channel, and it's been very convenient to have the needed games and savegames right by my side - no need to download stuff or re-complete the game, just install it, drop the savegame where it belongs and record the needed part.
have you ever lost your files and suffered because i didn't make a back-up?
Well, truth be told, it did happen several times... mostly because I didn't have enough money to by enough HDDs in time. Too much data to store...
Anyway, for the large amount of time, I didn't do backup of my system drive. So I lost my system... in a previous year, I believe, and didn't manage to restore all the files.
Frankly though, the pain was not in the files, but in configuring my system again from ground zero. I never really realized just how much of everything I've fine tuned over the years.
Since then I decided that I can go without another meal for a month or two, but to scrap enough money to buy an extra HDD to house a backup for my OS is imperative, and so it's been done.
how often do you do a back-up
It's pretty much on the fly process. Watched a movie? Into the archive. Scanned a book? Into the archive. Completed a video game? Into the archive.
And then every week or two I sync the backup drive with its twin.
