I believe that it should be made in an extremely clean environment such as a lab - where everything is sterile. Most of us don't really have that in our homes. Dust and whatever else happens to be floating around in the air gets into the liquid. For example, some people go into the bathroom, close the door, and shit, then just flush the toilet. When one does this, feces floats around in the air for about 2 1/2 hours - coating toothbrushes, hairbrushes, etc.. If one does this with the door open - the shit escapes out into the rest of the house - coating everything! (Closing the lid before flushing prevents this.) This is just ONE of things that can make a home too unsanitary for conducting such chemistry. You also gotta consider people sneezing, shit coming out the a/c vents, everyday dust in the air, etc.
I'm sure that it's just as effective, just not as clean. And from what I understand - gear has a "shelf-life" of 3 - 5 years. Don't quote me on that one, though. It's just what I've heard.