double post
Oxidation will eventually break down the compounds into simpler substances, thereby wrecking the flavor. And while indeed the hotness of the sauce will kill just about any bacteria, the accumulation of dead bacteria in your bottle of hot sauce does nothing for the flavor, either. 
Generically, they are Thai Chilis. But I’m sure there are some other varieties in the same shape/appearance that they could use in substitution.
They are one of my favorite parts of chinese food, and I like to grow them myself as well. I dry them, and crush for pizza topping, and also use them to make my hot sauces (a quart at a time).