The general suggestion for re-perming hair to fix or modify an initial perm that did not produce the desired results is between one to two weeks. The time in between the perm treatments should be taken to moisturize the hair and allow for the hair to normalize. A trained and licensed cosmetologist, however, may deem it safe for some to undergo another perming treatment earlier if the cosmetologist thinks that the hair has recovered enough from the initial perm treatment.
The process of cold wave perming basically exposes the hair to strong chemicals that break up the bonds, setting the hair to a desired style (either by curling or straightening) and then resetting the bonds back together. The chemicals used in the process can be quite harsh, and can make the hair dry and brittle. This is the reason that ample time in between perm treatments is recommended to allow for the hair to recover.
If one only seeks to maintain a particular hairstyle, the recommended time between perming treatments is six to eight weeks. Even for hairstyle maintenance, it is generally advised that the hair should be cared for with deep moisturizing treatments for several weeks before the perm treatment. Immediately before each perm treatment, it is advisable to take a hair strand test to see if the hair is ready for another perm.