I have a GSD bitch who is 3 years old, and has not had a season since april 2004,  in all respects she is fine, lively and happy.  the season in april was perfectly normal. has anyone heard of this before.

Inproper Thyroid function can abnormally effect the reproductive cycle.  What is her coat like, is eh lethargic, what is ehr weight like?

thanks for those comments.  she is shedding her coat at the moment, but normally looks good,  male dogs always seem to show some interest in her, I wonder if she could have a low lying infection, Vet says its not uncommon for dogs to have no season or silent season, perhaps will have to try a different vet, also was told she had very small kidney stones, could this have any bearing.  Have had a dog with pyometra and she is nothing like that, at present. and as this has been going on for some time, hope its not a possiblility. 

I have a Golden bitch who had silent seasons a couple of times -there was no bleeding and virtually no swelling, had I not had entire male dogs I would never ever have known she was in season. Eventually she was spayed and it turned out she was very very close to developing pyometra, so to play safe I'd have your bitch checked out by the vet.