I'd like to propose an archival practice.
The weakest spot regarding the longevity of recordable CDs is the lacquer surface. Fissures allow oxidization of the reflective surface.
Reinforced lacquer surfaces have become available. This reduces the surface vulnerability somewhat.
Gold does not oxidize. All other products used to reflect the laser light will oxidize.
Recordable CDs are available with gold reflective surfaces and hardened lacquer surfaces.
It seems to me that a gold reflective surface should be the accepted practice for any CD-R made for preservation purposes.
Lacquer reinforcement of the top surface is an added protection. Gold, however, should be considered essential.
Labeling of CDs should be clear when indicating if gold has been used or merely gold coloring added to another reflective product. I saw some of the latter in a computer store recently.