This is not true. GPS can flake on you, probably not the satellites, but I have seen more than one report of G1000 GPS failing, both of them. Apparently certain failure modes related to the antennas can result in jamming the GPS signal to nearby devices including the other GPS and nearby iPad GPS units.
This is not common, and admittedly I fly GPS nearly all the time. But if you have it at least know how it works and how to use it.
I think we've beaten this to death by now.