Actually mine just runs on batteries. I think they have an optical sensor which can be triggered by dust. I was told by support that they used to recommend blowing the debris out, but it wasn't good for customer confidence.
When your troubleshooting procedures remind your customers of their (erroneous but widely practiced) methods of making NES cartridges work, you might have a problem.
I don't know about NES, but at least with the N64, I swear by blowing into the cartridge. Works at least 75% of the time, and the other 25% by wiggling the cartridge a bit in the hopes of getting it to reseat better.
It works -- but what you're really doing is fixing an intermittent electrical connection by introducing moisture. Over the long term that's a recipe for corrosion.