I had a couple careers in computer operations and office automation. I know more than a little about preserving electronic data. Therefore I have multiple back-ups of my important files.
I don’t do it as often as I should, but intend to at least monthly. I save files from my most active computer onto two USB backup drives and onto my backup computer. If you are counting, that is four copies of every file I deem worth preserving.
With my mind working on a couple other things I copied my most treasured files onto one of the backup drives. Well, actually that is what I meant to do. Since this is a process I have been doing FOREVER I really didn’t need to focus. 
This time I copied the old file from the backup drive over the top of the current file on my desktop computer. *POOF* Data gone.
Unfortunately I had also been a bit sloppy about my backups lately. I lost about three months of data. Which brings me to the reason I share my folly.
GOOD BACKUP HABITS
Have at least three generations.
1) current on your computer
2) one generation old (weekly, monthly whatever you like)
3) two generations old (two weeks or months past)
Do NOT back up generation 1 and generation 2 in the same week/month
If you discover a file has been corrupted, you can go back one generation more to fetch an uncorrupted version.
Trade the backups back and forth
Perhaps one is labeled “ODD WEEK” or “ODD MONTH” while the other is labeled “EVEN”. Come up with some way that you backup you data over the oldest storehouse to maintain freshness.
You have to determine what value to place on your electronic data. If you put a lot of work and/or if it is very important, that is your answer. How much can you afford to lose? What is insurance against that loss worth to you in time and effort?
Of course Microsoft, Google and Apple are happy to store and sell all of your data. They not only back it up for you, but share it with commercial interests and dark forces worldwide.
