There are any number of problems that can develop with reel tapes that have been stored and any number of problems in playing them back to record if one does not play them at the proper speed or has dirty recording heads.   I have been overseeing a recording project for the past couple of years and we have managed to deal with some problems and failed at others.   I subscribed to ARSCLIST, a list for sound archivists for some direction.   We build a convection oven out of plywood and heated it with a light bulb to do the baking. As was said earlier baking is a solution to a specific problem, not all problems.   Tapes can be baked more than once but it makes sense to record them after the first time. Mitsui Gold, now MAM-A gold is recommended for archival storage.   One side of the disc is 24 k gold and the recording side has a special dye not commonly used in most commercial CD-Rs.   From what I have read the most damage to a CD other than physically marring the disc is oxidation and light.   The gold resists oxidation and the special dye supposedly resists light damage.   MAM-A rates the life span of their discs at 300 years.   That has yet to be demonstrated and there are reports that now that MAM-A discs are made in the USA and France they are not as reliable as before. There are also reports that hard drives that are put in storage can become damaged.   They are designed to be used. They have not been recommended for long term storage. The best bet seems to be CD-Rs and one should make several copies on different brand media and plan to migrate to the next media form in the future.   We also save MP3s as well as the gold and regular CD-Rs.