It must just be that the test solutions have a finite shelf life and it depends on whether the people at the store pay any attention to that, which I doubt they do. Personally, Red Sea has worked well for me without any problems. I am especially fond of the Seachem multi-test kits, because I can test all of my tanks at once, which is important. They are kind of stingy on the amount of test solution they give you, but you still get a pretty good number of tests off before they run out. I plan to use those from now on for phosphate and nitrate/nitrite tests, which I perform about twice a week on all my tanks.
Two 1 GA desktops, a 5 gallon, a 2.5 gallon, a 10 gallon, a 20 gallon, a 25 gallon, and two 75 gallon tanks, all planted.
I am an expert on algae, so ask me if you have questions. I know how to grow it, just not how to get rid of it.