Just out of curiosity, how often do you guys here back up files on your computer(s)?

For me, I back up at least once every 3-6 months depending on if I have major plans for my computer such as a reformat or just need to backup in case something major happens to the install of one of my computers.

I normally like to back up folders full of countless files monthly, and often my pictures and music after two (or not at all with the latter, dependent on how much my library expands.) External hard drives are one thing difficult for me to live without.

I don't specifically go out and back up files or create system backups on a regular basis, but my files end up all across my computer array anyway due to frequent usage. The thing I'm trying to do is to minimize duplicates so that there's only 2 copies of each file in my array in its entirety, which is very difficult since I've got thousands of files.

I back up every week or month, it just depends. I usually save my music and pictures, documents and stuff don't matter much to me because I don't use my computer for typing up assignments or essays. I upload stuff to my google drive (images) and then music to cloud.

I haven't backed up for a good four months now... and my only tool atm are a bunch of 16GB flash drives... If all these other expenses would stop cropping up, I'd buy a 1TB external hard drive and back everything up onto it instead of having all those flash drives floating around... Crossing my fingers that no major computer disaster befalls me before getting my external HD.

I really don't do a full back up as much as I should do. I'm lucky if I get around to doing it once a year.
When it comes to backing up small, important files I'll do it obsessively. I've already gone through at least three pen drives due to writing things onto them so many times.

I have an external 2 TB hard drive that my brother gave me to back up files that usually fall under the category of games, visual novels, music, anime, art, pictures, and music that I make and I usually try to back it up every month but I tend to get lazy and do it every 2-3 months

I had a hard drive fail once, lost everything, now I am paranoid.

I have my user folder re-directed to Skydrive, so all of my files are synced to the cloud, I do a system image weekly which I keep on an external Hard Drive, I keep that in in my car (its off site) So in the even my apartment gets destroyed, I don't loose any of the files that are too big for Skydrive, (mainly videos).

I make backups way less than I should... Hell, once a year is a lot for me. xD
EDIT: I store a lot of stuff in Dropbox though.

I use Time Machine (3TB storage via Time Capsule) to perform backups every week. I store some of my less important files inside my Dropbox folder though. Files that needs backup but not important enough to chip away some of that 3TB space. I also used to save my files within multiple USBs but that didn't go too well.

Time Machine, Dropbox, with USBs. Not a bad combination but I plan to move most of the files inside the USBs to my Time Capsule.

I tend to back up different files at different times. Financials I tend to back up immediately, school files I tend to backup every semester, and I try to back up my media (movies, tv, etc) every 3-4 months.

Skydrive seems to be my main backup, because there's not a whole lot of things I want to back up. Just pictures, roleplay documents, music, and other crap I store.

At the moment the comp I'm currently using has the hard drive backed up once a month, so that way all the precious memories my mom stores won't be lost. (even though they're backed up on facebook, it's always to know they're safe xD)

I didn't start backing up my files seriously till a few weeks ago. I began to take the back-up thing seriously when my PC "broke down" last month. I was worried it could be something important and began regretting not to have backed up all the files. Fortunately, I found out it was the power supply, and I only had to replace it for a new one and my PC started working again. Since then, I make sure to back up every single file I consider is important (such as music, TV shows, everything I code (which is the most important), games) in my 1 TB external hard drive. Now, I feel safer.

I'm a bit OCD about backups: I use Time Machine to back up everything once daily.

I don't back up at all currently X_X. I have a 2TB drive which stores all my DATA and a 1TB for my operating system. If I need to reformat my O/S then it can be easily done. I recently upgraded to Windows 8 which is stable for now. Hard drives just suddenly failing is quite rare since you can use SMART tests to see when a hard drive is slowing down and may fail. So in that case you can rush out to get a new hard drive !
Trying to back up almost 1TB of DATA is not going to be fun...I may just buy a 3TB internal drive to back up onto.
Also if you upgrade your computer as much as I do (upgrade every 2-4 months) normally things don't get a chance to fail ^_^