I agree with keeping the footage on DV.
Just buy a whackload of miniDV tapes, and copy your old tapes (VHS, Hi8 or whatever) onto miniDV by recording using the A/V inputs of your miniDV camcorder. Use the s-video input if the VCR or other tape source supports it. Then label your miniDV tapes and put them in storage somewhere cool and dry.
Later if you need access to the footage, it's all right there in your DV tapes. If you should ever fear tape degradation, you can always make a 100% digital copy from miniDV to SuperDuperHiDefPurpleRayVideo or whatever the new standard is 5-10 years down the line.
DV footage, at the equivalent of 13 gigs per tape (~$5 or so?) still rivals hard drives and DVD-R's for cost effectiveness, and is certainly much more convenient than trying to burn the raw DV footage onto a DVD-R (you'd need about 3 discs per tape).
You could buy a large hard drive and digitize all your tapes onto that, but I would have reservations about how long the drive would last and if it were to fail, you'd lose it all.