I know of people with "CFS" (but which type?) who have recovered. I also know of a few who recovered, went back to a normal life, and then relapsed very badly. One of those has never recovered from the relapse and is much sicker than they were the first time.
I think full recovery is theoretically possible, and does occur sometimes, but I also think many cases of "recovery" may be linked to misdiagnosis, and that its more accurate to talk of remission than recovery. Its also likely that many recover partially and adjust their lifestyles and management of their illness so they can live a nearly normal life. So long as they look after themselves, this often continues.
There is also the issue that most cases of post-viral fatigue disappear within six months to five years. Such fatigue is most probably not ME. These cases are often diagnosed as CFS, and from the Dubbo studies we know that about 8-12% will actually go on to develop a CFS-like condition. The Dubbo studies did not use an ME definition, so this is less robust of a finding than I would like.
Under an experimental protocol I was on in the early to mid 1990s, about 60% of patients experienced partial to full remission .... but only while on the protocol. Further the long term risks of the protocol were hard to assess. However about 10% of these appeared to no longer need treatment. This again used a CFS definition, not an ME one, and the protocol was never operationalized for mass use, and was hideously complex but not expensive. On the downside about 20% had no benefit, and about 10% got worse. This data excludes smokers. Zero smokers improved under this protocol. It was primariliy a dietary protocol featuring precision control of fat intake and a natural food diet. I was on it for some years, but only had small improvements that persisted, though short term improvements were considerable. I think I actually declined on this diet over time ... the short term gains were more than countered by long term problems. Run a search on Gray and Martinovic and CFS on PubMed and you will get one of their abstracts.