Reliable backup, particularly for long durations, is still very much a black art. There are a lot of considerations, the two main ones being reliability of media, and its accessibility.

I personally would go with high quality DVDs, a good burner, PAR2 parity, and a decent place to store it. Treat your hard disk as some kind of LRU cache. Use the DVD C1/C2 counterpart to do a yearly scan and copy data off dying DVDs.

You may want to also burn copies of the necessary extraction tools onto the DVDs, like the archive program you used, necessary codecs, QuickPAR, etc.

Once DVDs start being replaced by a newer media, much like CDR's are now, move everything across.