Since the condition is classified as chronic, many who have it never really get over it. I’m not sure if “relapse” is the right word. Also, there is a lot of individual variation.
Here is a study related to that question which might interest you:
Long term prognosis of chronic inflammatory demyelinating polyneuropathy: a five year follow up of 38 cases:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2117396/#!po=23.6842