Well you've answered your own question really, ie cheap parts = cheap quality = may not last very long!
With some companies though and their repective pattern parts there's no reason not to buy depending on the actual part and knowledge on places like this forum as to what is ok and what isn't.
For less expensive or critical components/parts i tend to stick with a VW main dealer.
A pattern part may look identical to it's VW counterpart but with the former the manufacturing process will have been less costly..and that means lesser quality components/metals/plastics..along with a less stringent R&D and Testing/quality control/cheap labour etc.. so, that's why they're cheaper and that's why in many cases they fail at some point too soon.
Of course, you can always get a dodgy batch in either..
Having said all that, i bought an ABS sensor a year ago from gsf and no problems, i guess it might last another year according to your time failure..
