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).

Somewhat related is that I have several gigabytes of uncompressed recordings in .wav format, which I have backed up, but still don't feel good about deleting, even though I could use the disk space. I have a serious dislike of destroying data, even though in this case it is far from actually destroyed in any sense other than its section on one of two disks is marked as available.

I seem to recall hearing about some service that can automate backups. I would have to investigate the security/costs/CPU usage/etc, but it sounds like it could help some people get around the trivial inconvenience of actively backing up data.