"Also a related question.I also read somewhere that DVDs are not a reliable storage medium." A load of tosh. If unused and safely stored they can last 20 years and still work happily.
A hard drive I once read is good for about a million million (1 with 12 zero's) spins. About 4.5 years of non stop spinning. So really it depends which you trust. If you make 2 copies of a DVD and one goes dead you still have a back up. Buying a hard drive and if it dies you loose everything. I would certainly rather loose just one DVD rather than all of them on a hard drive (and these do fail). I lost all my data to a failed hard drive in a machine that was 3 months old.
It is up to you how you save them. Once option you could consider is however using one of the above and an online file storage system. Prices are pretty cheap and on a per month basis. Access worldwide guaranteed safety of the data.