Yes Dee,the average life span is 12 years old.
BUT,they can live to be 15,if not older.
My previous GSD was 13 and I had to put him down.If it wasn't for his hips,he would have lived longer.He was quite healthy and still had puppy in him.
Not sure if you have read Iggette's previous posts.But she just lost her beloved Bandit.
As for suggestions Iggette,I wish I can help you.But what I do know is,at shelters,like our SPCA here they want you to bring in the dog you have to see how another would interact with it.
I'm sure LR,Luba and Carina with the rest of the gang can help you.