|IMO the best current method is to burn them to CDR or DVDR. Burn at a slower speed. That should insure a better disk.|
Once you make a disk you can cheaply make multiple copies. Date and label the disks. Spread them around to preserve them and every couple of years make copies of the disks.
Check the file integrity of the originals and the copies. Be sure to know what is on each disk. Searching blindly can take forever. Use folders with descriptive names. Possibly have a catalog file also on the disk.
These files are irreplacable, treat them as such. Safety deposit box is a good place for one copy. You need to get the second available size. The smallest is not wide enough.
OfficeMax sells cheap paper sleeves for optical disks. They take much less room than jewel cases.
There have been many articles written about the life expectancy of optical media. I think the key is to store in a stable environment. No light, normal humidity, etc.
One last thing to mention. Label what the type of disk and the density. 20/30 years from now the hardware will be different and users then will need to know how the disks were originally created. Might not hurt to even mark the file extension used.