Many tapes are found to have degraded; a technique for rendering some of these tapes playable involves controlled "baking" of the tape. Unfortunately it appears that some folks, including some people responsible for irreplaceable original assets in the music industry, may have adopted a habit of baking all old tapes. Please do not bake tapes indiscriminately. Permanent damage is done and as such, the process is to be employed only when concluded to be necessary.
This article specifically lists which tapes are affected by what issue and whether or not baking should be considered:
Article regarding degrading tapes from expert Richard L. Hess.
This article discusses some of the issues:
Notes regarding tape baking effects from expert Charles A. Richardson.
The problem in many cases involves the substitution of whale oil and/or improper storage conditions. Yes, whale oil. Whale oil was widely used as a lubricant agent in quality magnetic tape manufacture and has proven to be impervious, thus far, to age provided the tape is stored in good conditions (a cool, dry and stable environment with low humidity - such as existed where tapes including those of Nat King Cole used to be stored at the Capitol Tower in Hollywood California). Bans on whaling c1973 obliged a switch to alternative artificial substances. Those substances have had, let us put it, mixed success in terms of affecting a tape's shelf life.
So in summary: Quality tapes prior to c1974 (happily that includes all of Nat King Cole's original tapes) are not affected by the issues baking is meant to address and should as a rule never be baked. Only those made thereafter would likely require it and should be approached as if they may never be playable again; so if successful, while it is playable the finest straight dub to analog and digital media possible should be considered.
All that stated, the originators of the baking process were Ampex, whose (expired) patent on the process indicated an optimum baking condition of a steady 129° (degrees) Fahrenheit for about 8 hours, with a relative humidity of 15 percent. This is a dangerous temperature for tape so one must be careful heat is even not resulting in excess and controlled with care. One may have days or perhaps a month to transfer the tape depending upon the tape and environment (humidity etc) present. Again: first ensure it is the correct procedure and absolutely necessary for that specific tape.
Long may the reels turn for you.