I have the same problem. Worse is that I kinda need to leave my computer to do the backup for upwards of a few hours, making it slightly more inconvenient. I know I haven't done a backup since my last major update to my commercial game, so if I lost my data right now, the source code would be gone (the compiled program itself is backed up in a secure location).

Suggestion: if you haven't by the time you read this, do a backup of that source code right now. Leave backing up the rest of your computer for another day if necessary.