I personally have not Mandy, but I have met a number of people over the years who have suffered chronic fatigue as a result of mono. The most recent one is a close friend of mine who recently burned the candle at both ends a bit too much - very much a non-stop go person - and brought on a relapse of her long-distant, mono-related fatigue. It took her several months to get over it; I can't remember how long she was signed off work for but it was weeks if not getting on for months. However she is now back at work, and has just come back from month's holiday in New Zealand, canoeing, walking and hang-gliding.
So I think that's pretty much "cured" there...
The tales I have heard previously from other mono sufferers typically talk of a period of severe fatigue after the initial illness, which extends for a period of three months to a year or more (dependent on severity of illness, attempts to ignore it, original health etc) and during which there is a marked decrease in immune system functioning, leading to an increase in opportunistic infections. However given the appropriate treatment - which I think is supposed to be a specific type of antibiotic followed by complete rest for a number of weeks, ( but don't quote me on that, my info is old and those details may be wrong ) a pretty much complete recovery can be expected. You didn't say why you were asking, but I'd guess that's what you were wondering about.
The reason for the confusing information you have found on the Web is due to the debate about what causes chronic fatigue. It is a notoriously grey area as all sorts of ailments - darn near all of them really ! - can cause fatigue, and there are as yet no cut-and-dried tests or biochemical markers that can be used to say what is and is not "chronic fatigue". There does seem to be split between some types of fatigue which are post-viral (like mine) or post-some-kind-of-illness, and others which seem not to be; but you can also split cases up into also-have-opportunistic-infections, and don't-have-opportunistic-infections. And to add more spice, in cases like that of Myalgic Encephalopathy (M.E.) there is also a wide range of well-defined neurological symptoms, which are however not well used as diagnostic criteria. And in America everything tends to get lumped under the umbrella term "Chronic Fatigue Immune Deficiency Syndrome, while in Europe and the UK the debate rages about Post-Viral Fatigue Syndrome and whether M.E. is caused by one trigger or many, etc etc.
Clear as mud. If Chronic Fatigue was a church, there would be about a dozen different pastors, each with their own congregation. And of course it's a medical Catch-22; you can't research an illness that is not properly diagnosed, but how do you diagnose this illness without more research ?
Happily, mono is unique, in that there is a diagnostic test which confirms that you have mononucleosis, and a very specific treatment regime for that trigger. So you have a "get-out-of jail-free" card on that, which most chronic fatigue sufferers do not.
The main thing to remember is that if you do overdo things mono is inclined to come back - though not so badly - and the best treatment is rest in the sort of quantities that would drive a contemplative monk bananas.
Hope this helps.