I separate everything in years. Current year gets synced every week via rsync with a drobo (drobo duplicates the data amongst all the drives). I also have a disc in another location that gets synced once a year at christmas with the archive. It was a bit of an investment but then it's pretty cheap to run.

I know it's not perfect. If I delete something without noticing and sync it afterwards it will be lost forever, but I'm running this for the last 10 years and never really had a problem.