If scientific skeptics indeed use empirical investigation and the application of the scientific method to determine truth....does that mean we're always right? If so, can this be repeatedly demonstrated?
Scientific skepticism is a process designed to reduce the number of errors made. However, there are copious ways in which scientific skeptics can be lead to provisionally accept incorrect conclusions. I don't believe any prominent skeptics claim that they are always correct because of their skepticism.
(I would argue the more important thing to define skepticism is what happens when the mistake is realised.)
Some error sources include:
Forgetting to "carry the one", missing a logical fallacy, confusing definitions, emotional biases, cultural biases... anyone can make a mistake.
Ultimately, science is supposed to be able to detect the errors introduced due to fraud when efforts to reproduce the experiments fail. Nonetheless, this can take years, and in the meantime, the false evidence may mislead.
The Piltdown Man is a classic example of this.
Science can reveal more details that invalidate earlier models. (Newtonian versus Einsteinian models of physics are frequently cited here, but I've always bristled at the suggestion that Newton was "wrong", as though his model wasn't incredibly close and still very useful.)
A lot of hypotheses are supported by statistical outcomes of experimental models, which are subject to noise. As sample sizes grow and experimental techniques become more accurate, the new data may overturn old conclusions.
Science depends on studying the natural. If there is a malevolent God (or other supernatural being) that is deliberately making the natural world look to skeptics like it follows one set of laws of nature, when it is actually more capricious that that, we should expect to be wrong a lot. Skeptics reject arguments like this as unfalsifiable, but unfalsifiable doesn't mean it is wrong - merely that it is unproductive to discuss and investigate.
Scientific skepticism, in theory, is designed to reduce the amount of incorrectness caused by Type 2 errors - that is a fancy way of saying "believing something is true when it isn't".
In other words, someone practicing scientific skepticism is more likely than someone who is not to correctly identify an invalid claim as being invalid, instead of blindly believing that claim to be true.
That is, of course, just one way of being "correct" - there are also Type 1 errors where you disbelieve a valid claim (which a skeptic is MORE likely to make as an error); as well as simply being wrong for other reasons that @Oddthinking's answer covered in detail.
Side complication: please note that in some narrow circumstances,
... scientific skepticism CAN easily cause one to be on average less correct than absence of one. For example, if proverbial "they" are out to get you, being a paranoic is correct; while being scientific skeptic would likely cause you to err by assuming nobody is out to get you due to absence of proof.
... scientific skepticism CAN be counterproductive in a larger picture. If you're in a savannah, the cost of Type I error is being eaten by a tiger you skeptically rejected as you haven't seen one; whereas the cost of Type II error you didn't make as a skeptic and your un-eaten nonskeptic friend made, is quite low in comparison. In other words, skepticism isn't always a survival trait - which is why human brains work the way Kahneman and co... posited and not the way answers on Skeptics.SE are supposed to.
It's quite tempting to divide our knowledge between "correct" and "incorrect" concepts, but I personally find it philosophically problematic. The real world is not built upon correctness and black-and-white categories. Those are human labels which often don't quite match the world.
Scientific skepticism is not about "categorizing" knowledge into two big piles of "right" or "wrong" ideas. It's about understanding the available evidence that supports or refuses such ideas. Is there strong evidence for a claim? Weak evidence? No evidence? Evidence against?
In turn, the most extreme of these cases will correlate with "correct" and "incorrect", but this kind of labeling misses the point, which is a nuanced view on reality which includes accepting there's stuff we don't know, stuff that we accept as true without proper evidence, stuff that we actually know and should stop debating, etcetera.
This kind of nuanced thinking also applies to the concept of temporary truths: the things we accept as true temporarily while we investigate. Do alien UFOs exist? I'd assume not until proven otherwise. Does extraterrestrial life exist? I'd assume yes until proven against. Clearly both of these statements are mostly based on personal assumptions, but are also valid skeptical positions, simply because lack of evidence is a valid skeptical position (often also called null hypothesis). Does this make any of these statements "correct"? Nope, but that's missing the point. There's stuff we accept temporarily without proof and that's OK, as long as we change our minds based on evidence.
Compare this with the opposite of scientific skepticism: absolutist thinking. Stuff is accepted to be "correct" in absolute terms without the very high levels of evidence that skepticism would require. For example, people that strongly believe in a religion will claim that their divinity exists in absolute terms, as a matter of faith, even though there's no credible evidence in favor or against. Whilst this is clearly OK in general terms—everyone can believe in whatever they want—it is not a valid skeptical position. At best a skeptic could accept a divinity as a temporary truth, although most do probably accept it as temporary falsehood.
In conclusion, repeated application of the scientific method leads, over time, to more evidence and more likelihood of repeatability: something that happens reliably might keep on happening. We know that from the fact that science works quite well. One might say this leads us to "correctness", but for the vast majority of ideas the evidence is not very strong either way and we need to honest about it and not categorize them in such strong terms.