There are two parts to this backup thing ... are we talking about backing up the OS or the data? Cause, they are very different, and require different strategies. I have not made any backup of my OS for months (but I do restore it quite frequently). I backup my data everyday. Doesn't everybody?
The prep below sounds complicated. But in use, life is easy for me. I have one computer that gets infected with virus very often (because it is used by customers, who bring their own flash drives). Every time that happens, I run a program that automatically restores the OS. The program asks for no input. I run it, go get coffee, and 5 minutes later, the computer is good as new. It's my own "restore to factory default", but instead, restores the computer to exactly how I want it to be, everything already set up, and it is ready to use. My other computers, require OS restores less often, but when they need it, it is extremely easy to do.
Before I can do this, of course I have to plan in advance, by splitting the hard disk into different partitions. The OS goes to partition c:, d: is for the swap file, data goes to e:, f:, g:, etc. Never save anything to c:. Size the partitions according to need. How big c: needs to be depends on the OS (Win7-32, about 20-30GB. XP-32, about 8GB). It should not be too big, because we will then need more space to store the backup itself, and both the backup and restore process will take longer because there is just more stuff to copy.
I install Windows to c:, install all the drivers, configure and tweak the computer to exactly how I want it, install my "essential programs", turn off system restore, delete all unnecessary stuff, empty the recycle bin, defrag the hard disk, and make an image backup of c:.
The backup/restore is done by a Linux program called partimage, called by a simple short shell script. Use either grub or partimage to select which partition to boot to. Semaphore files indicates to the shell script whether to do a backup, a restore, or just start bash.
Even if you don't have my somewhat complicated set up, you should consider separating the data and OS. Saving stuff in "My Documents" in c: is just asking for trouble. At some point, if your computer cannot run properly and you need to reinstall Windows, it would be extremely difficult to try to figure out exactly how you get all the data off before you reformat that hard disk. Especially if you do not have a second (working) computer to do this on. If all the data is on a separate partition, you can just reformat c: at any time.
The data backup is based on btsync (now called Resilio Sync). It is nearly completely automatic. If I edit any file, it would automatically get synced to the other computers. I go to work, all the files I need are there. I go home, they're all there and up to date. When a project is finished, I zip them up to reduce the file count (when file count goes to the high hundreds of thousands or millions, syncing slows down and consumes more resources), and move them to an archive folder (which is also synced between 3 computers for backup).
However, some files that change very rapidly while I'm working on them are not suitable to be synced this way (because Internet speed is not unlimited, and the sync program could cause locking problems). For these, I make a working copy on my hard disk. At the end of the day, I run FreeFileSync to mirror the working copy back to the sync folder.
Note that FreeFileSync is different from btsync in that it syncs between two folders on a single computer. btsync is a cloud sync program like DropBox, but without the server and without capacity limits. It also automatically does a sort of versioning by moving old versions of files to a special location.
For cloud sync to work properly, you must ensure that all your computer clocks are accurate, and set to auto-sync to a timeserver. If they go too far off, you could have data loss. Eg you edit some stuff at 4:50pm, go home and continue your work at 5:50pm, but the clock is two hours off and it actually says 3:50pm. The sync program looks at the timestamps on the file and gets confused as to which is the newer version and which one you want to keep. It will keep the other version in the backup location, but you may not notice the problem and so don't correct it until after you've zapped the backups to reclaim hard disk space.
And of course, you don't sync everything. Only stuff you want to backup. For example, I don't sync 5GB movies I downloaded to watch, because that'll choke up my rather slow Internet connection for hours. We can set bandwidth limits on btsync, but that will only mean the stuff we want to sync will take longer to sync up, if there are a couple of extra large multi-GB files in the queue. If I really want to have those large files at work and at home, I copy them to a portable hard disk and hand carry them.