Are there symptom changes and different phases to the illness or are symptoms constant? Within this question it may be that a lot of symptoms are constant but some change. I've noted that people do talk about different symptoms when they are first ill or perhaps more varied symptoms that settle into more of a pattern but then occasional changes.
I also wonder about people who have a gradual onset where symptoms are initially occasional after a particularly busy time but then something like a virus triggers a much worse state where symptoms are much more severe and there all the time.
One thing I wonder about the 3 year thing is it a gradual change over time with a crossing point at 3 years or is it more of a phase change around the 3 year mark. I noted they said:
For cytokines that differed between short- and long-duration groups, levels were correlated with duration of illness, and in the expected direction: inverse correlations with duration of illness for cytokines that were increased in the short-duration group, and positive correlations for the two cytokines with reduced levels in the short-duration group (CD40L and PDGFBB) (table S7).
But I wasn't sure if that meant correlation by duration within each of the groups or whether it was across the groups.