The average onset of CFS is middle-age, so for the average patient, they do not need to compare their recovery to some romanticized version of their wild youth. Most people settle down a lot between the ages of 20 and 30 anyway.
Table 1 of the 2011 Lancet paper shows that the mean(SD) age of participants was 38(12) years at baseline, and the median(IQR) of illness duration was 32(16-68) months. So for most participants, pre-illness was not some mysterious archaeological age which they can barely remember, it was only a few years ago.
Yes, some of us have been ill much longer and became ill in our youth but are much older now. What we should personally expect from a "recovery" is to be able to feel how and do what people our age are feeling and doing, relative to our natural abilities and limitations of course. I do not think the average 40 or 50+ year old patient is seriously going to expect being able to work and play as hard as they did when they were 20 or 30 years younger.
Judging from the several small studies I have seen which used healthy age-matched controls for their study participants, what is "normal" is no significant fatigue and scoring at or close to 100% in physical function. Scoring 5 (bimodal) or 18 (Likert) in fatigue and 60 in physical function is not normal for healthy 40 year olds as PACE would have us believe.
Getting 640 healthy age-matched controls for the PACE Trial would have been ideal, but even if White et al just
properly analyzed wider population data from genuinely healthy adults of the same age as the PACE Trial participants, they would have come up with much better thresholds for normal. Instead for example, the threshold for normal physical function has been plagued with several amateurish blunders which undermine their credibility as "experts".
OK, so what about the minority of healthy people in the population who experience some transient fatigue? Common reasons include over-work and lack of sleep. CBT/GET should have addressed some of the problems causing fatigue in healthy people. Like some patients I do have a few grand fantasies about what I should be doing if I was healthy, but in practical reality I do not expect to be absolutely and perfectly free of anything resembling minor symptoms. I am in the early 30's so I do however expect what is usual for my age group, relative to my own natural abilities and limitations.
I suspect that the trap for the average long-term patient is not unrealistic expectations about recovery, but mistaking (or pushed into believing) a significant improvement for a full recovery. As Bob indicated, some patients may have forgotten what they are really capable of, after years of adapting to pervasive impairments. Compared to a PACE "recovery", a genuine recovery may be like waking up for real after a
false-awakening in the dream state.