There have been several prognosis questions recently, so what follows is my attempt to speak to those questions without speaking to any individual person's prognosis, which is impossible for me to do. I hope this is helpful!
Disclaimer: This is not medical advice. This is not meant to be, nor should it be construed as, prognostic information specific to your case or in applied to your own case. The best place to find out about your individual prognosis is from your own physician and/or an autonomic expert who is well-versed in your individual case.
That being said, here are some very general things that have been noted in research on dysautonomia. There are only two forms of dysautonomia known to shorten a person's life-expectancy; both of these are (fortunately) very rare. One of these, familial dysautonomia [FD], is congenital (present from birth) and basically (anomalous cases have happened, but that's so rare compared to the human population it's almost not a consideration) only occurs in children where BOTH parents are of Ashkenazi Jewish heritage. The other, multiple system atrophy, generally onsets in the later decades of life and can sometimes be diagnostically confounded with Parkinson's.
Those aside, one thing to realize is that some forms of dysautonomia are primary and some are secondary. A secondary dysautonomia means that the autonomic dysfunction is a "feature" or an "effect" of some other underlying disease, condition, toxicity, etc. I do not have room here to list every form of dysautonomia, but I'll try to hit some highlights to paint a general picture. Here I'm using the classification system put forth by Prof. Christopher Mathias in his texts (top autonomic doc in the UK, one of the top autonomic specialists in the world).
There are a few acute primary dysautonomias, one example being Pure Cholinergic Dysautonomia; chronic primary dysautonomias are represented by Pure Autonomic Failure and MSA, for example. The bulk of dysautonomias are secondary. With secondary dysautonomia, the thing to keep in mind is that the prognosis of the dysautonomia is dependent upon the prognosis of the primary diagnosis. As an example, take Vitamin B12 deficiency: usually, replacement therapy will alleviate the orthostatic hypotension. So sometimes in secondary dysautonomia, if you can find the cause, you can simply treat it and the dysautonomia symptoms will entirely resolve. However, familial dysautonomia (hereditary sensory and autonomic neuropathy type III) is also considered a secondary dysautonomia, and so far there is no cure for this; on the bright side, supportive treatment for FD has improved considerably over the last 5 decades or so, such that people with FD are now reaching adulthood and even having children of their own (because it is a recessive gene, their children do not get the disease, though they will be carriers of the gene).
In terms of POTS, if you've read my "POTS is a syndrome not a disease" speech 90 times before, skip this paragraph. If not, here we go ... POTS stands for postural orthostatic tachycardia SYNDROME and the word "syndrome" has a special meaning in medicine. In short, doctors know that there are a set of signs (objectively observable and measurable phenomenon like blood pressure and temperature) and symptoms (subjective phenomenon that only the person who experiences them can report like nausea, dizziness, and fatigue) that tend to occur together in a specific pattern in patients. However, they call it a "syndrome" because it doesn't meet the criteria for disease in one important way: doctors and researchers have not identified an underlying cause. Now, that leaves a question waiting in the wings. Is there ONE cause that leads to all cases of POTS and they're just not finding it, or are there lots of different causes that can lead to this same syndrome? Some experts in POTS have spoken up in favor of the multiple causes hypothesis, others are still looking for a cause or waiting for more research on POTS. One cause of a relatively small number of POTS cases has been identified in NET (norepinephrine transporter) deficiency, but this speaks to such a small portion of POTS cases that it is only the tip of the iceberg in terms of finding an answer to what causes POTS.
Still, even without knowing the exact cause of POTS, or even whether all POTS patients have the syndrome due to the same underlying cause, some observations about prognosis have been made. One important note is that, for the purpose of the case studies on prognosis in POTS (at least the ones I have seen), researchers and physicians consider a patient to have made a "recovery" if the patient is able to return to functioning in life (participating in work, school, etc.), even though this may include having made some lifestyle adjustments to allow this to occur. Which is to say, there are a number of patients who find that this definition of recovery is not in line with their own definition of that word (or hopes for recovery), which may be more along the lines of being returned fully to the pre-disease state (i.e. "cured"). It is also important to note that because POTS is a relatively "new" condition (having only been recognized and named by doctors recently, even though it surely *existed* prior to that, and indeed seems to have possibly been treated under other names in some cases historically), we just don't have as much long-term data on POTS patients as we do about patients with other diseases. Without that data, our understanding of prognosis will be necessarily weak.
That being said, here's some information on POTS prognosis. A number of patients do make a recovery (I'm not willing to hedge bets on the percentages they throw around, because I don't think the data is sufficient to support it), generally within 5 years of onset. Patients most likely to make a recovery are those with childhood onset POTS. (Anecdotally, I've heard of recoveries in childhood onset POTS cases after spans longer than 5 years; part of this may be that doctors are getting better at identifying POTS in younger children so it's taking relatively longer to "outgrow" from time of official diagnosis. It's hard to say.) Some report that viral onset POTS patients are more likely to make a recovery than other subsets as well. Those with JHS/EDS generally do not have as high of a likelihood of recovery. (Personally, I would class this under a Secondary Dysautonomia, and thus it would follow the rule of the dysautonomia following the prognosis of the primary disease, that being the Joint Hypermobility Syndrome.)
Please feel free to follow up with any questions and I'll try to answer to the best of my ability. If anyone has questions about a dysautonomia I didn't cover (or skimmed over) here, let me know. Thanks!