
I don't know who told you a long-coated GSD will not moult as much as a short-coated dog - but they are wrong. Length of coat has nothing to do with moulting.
Your bitch will shed twice a year with the seasons - and she will also likely blow coat with her own female seasons if she is not spayed. The coat can look real dull and patchy.
I had a very plush coated GSD years ago and she literally never seemed to stop shedding. It's not typical, but it does happen with some dogs that there seems to be no end to it. When I got really fed up I'd take her to the groomers for a wash and brush out - they would always apolgize to me that they brushed her for a long time, but could not get all the loose hairs out. I never told them it was impossible! :-) All dogs lose hair throughout the year, of course, even the "non-shedding" breeds. The more coat, the more this is going to be noticeable.
How often do you groom them? If you do it frequently (daily) you can sort of speed up the moulting process by making sure the dead and near-dead hair and undercoat is removed as soon as it is ready.
Diet can also help to slow down hair loss sometimes. Plus, going in and out of a very cold environment to a heated environment can increase hair loss. Although in this country the temperature extremes are no so great that they should play a huge factor, especially at this time of year.